fcr.iop.org

Volume 1 Issue 4 Dec/Jan 2005Can theory improve fuel cells?Precious metals and recyclingThe infrastructure conundrumToyota: secrets of innovation

An IOP Emerging Technology Review

THE

FUEL CELLREVIEWCOMPETIT IVE INTELLIGENCE ON HYDROGEN AND FUEL CELL TECHNOLOGIES

Will carbon nanotubes be the next big thing?

ISSN 1743-3029

THE

FUEL CELL REVIEWVolume 1 Issue 4 December 2004/January 2005

Clean up the atmosphere p6

Fuel-cell locomotives on a roll p32

A disruptive take on DMFCs p33

5 News & Analysis

NASA puts the spotlight on fuel-cellresearch ● Atmospheric scientists want to see more HEVs ● Up, up and away for DMFC fuel cartridges ● MCFCs go to work in Tokyo ● Toyota banking onnanomaterials ● Sustainable hydrogen

11 R&D Focus

An easier route to metal-oxide films ● Unique behaviour has potential forhydrogen storage ● Compact cooling unit can mimic plant biology

13 Patents

PEMEAS ● ABB Research ● ToyotaCorporation ● Entegris ● Commissariat à l’Energie Atomique ● UTC Fuel Cells ● Forschungszentrum Jülich ● Stichting Energieonderzoek

29 Technology Tracking

Carbon nanomaterials: what can they dofor you? ● MEAs just got more durable● Precious-metals recycling makes a lotof sense ● Fuel-cell locomotives: on the right track ● DMFC membranes

34 Talking Point

Robert Rose, executive director of the USFuel Cell Council, lays out the game planfor a visionary public-private partnership to accelerate the volume acceptance offuel-cell technologies and applications.

15 RESEARCHCan theory help to improve fuel cells?MICHAEL EIKERLING, ALEXEI KORNYSHEV

AND ANDREI KULIKOVSKY

Theory matters – it matters a lot. As such, a soundtheoretical framework should not be viewed as atime-consuming diversion, rather as the bedrock of fundamental innovation and optimization infuel-cell materials and components.

25 INVESTMENTHydrogen infrastructure: why, when, how?STEPHEN LASHER AND STEFAN UNNASCH

The creation of hydrogen-fuelling infrastructureswill require decades of investment and innovation.The latest studies from the US shed light on thecommercial challenges associated with hydrogengeneration, distribution and storage.

DEPARTMENTS FEATURES

Cover: Computer models of single-walled nanotubes p29. (Courtesyof Thomas Swan & Co Ltd.) The images were produced with MaterialsStudio 3.0 (from Accelrys Inc) by James Elliott, Materials ModellingGroup, Department of Materials Science and Metallurgy, Universityof Cambridge, UK. E-mail: jae1001@cam.ac.uk

THE FUEL CELL REVIEWDirac House, Temple Back, Bristol BS1 6BE, UK.Tel: +44 (0)117 929 7481Editorial fax: +44 (0)117 925 1942Advertising fax: +44 (0)117 930 1178Web: fcr.iop.orgE-mail: fcr@iop.org

ISSN 1743-3029

EDITORIALEditor Joe McEnteeTel: +44 (0)117 930 1016joe.mcentee@iop.org

Contributing editors Susan Curtis,Belle Dumé, Tami Freeman, SiânHarris, Hamish Johnston

Senior production editor Lucy FarrarTechnical illustrator Alison Tovey

ADVERTISEMENTSKey account manager Simon AllardiceTel: +44 (0)117 930 1284simon.allardice@iop.org

ADVERTISING PRODUCTIONAdvertising production editor TanwenHafAdvertising production Katie Graham

SUBSCRIPTIONS AND MARKETINGSubscription and fees managerJenny Brown

ART DIRECTORAndrew Giaquinto

PUBLISHERGeraldine Pounsford

PUBLISHING DIRECTORRichard Roe

SUBSCRIPTION RATES 2005Individual subscriptions:£149/$269/€219 per annum.Library subscriptions:£350/$629/€509 per annum.Bulk copy subscriptions are alsoavailable. To subscribe, pleasecontact us at:Tel: +44 (0)117 930 1034Fax: +44 (0)117 930 1178E-mail: jenny.brown@iop.org

US MAILING INFORMATIONThe Fuel Cell Review (ISSN 1743-3029) ispublished six times a year for $269 by Institute ofPhysics Publishing, Dirac House, Temple Back,Bristol BS1 6BE, UK. Periodicals postage paid atMiddlesex, NJ 08846. POSTMASTER: sendaddress corrections to The Fuel Cell Review, c/oPO Box 177, Middlesex, NJ 08846. US agent:Pronto Mailers Association Inc, 200 WoodAvenue, PO Box 177, Middlesex, NJ 08846.

Copyright © 2004 by IOP Publishing Ltd andindividual contributors. All rights reserved. IOPPublishing Ltd permits single photocopying ofsingle articles for private study or research,irrespective of where the copying is done.Multiple copying of contents or parts thereofwithout permission is in breach of copyright,except in the UK under the terms of theagreement between the CVCP and the CLA.Authorization of photocopy items for internal orpersonal use, or the internal or personal use ofspecific clients, is granted by IOP Publishing Ltdfor libraries and other users registered with theCopyright Clearance Center (CCC) TransactionalReporting Service, provided that the base fee of$2.50 per copy is paid directly to CCC, 27Congress Street, Salem, MA 01970, USA.

The contents of this magazine do not representthe views or policies of the Institute of Physics, itscouncil or officers unless so identified.

Printed by Warners (Midlands) plc, Bourne, Lincs, UK.

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

NEWS &ANALYSIS

Also in this section

6 Atmospheric imperatives

7 Micro fuel cells flying high

8 Stationary power in Tokyo

9 Toyota talks innovation

10 Clean, green hydrogen

The heavens can’t wait

The US space agency NASA is looking toboldly go with renewed purpose and direction(as well as hefty financial backing). An ambi-tious agenda, covered in a new SpaceExploration Initiative, lays out plans to increasethe use of robotic missions to improve under-standing of the Solar System, to develop ahuman presence on the Moon, and to followthat with a manned mission to Mars. The ini-tiative has been developed in response toPresident Bush’s overhaul of the US space pro-gramme, unveiled in January 2004. NASA nowhas three main goals: the completion of itswork on the International Space Station by2010; the development of a new crew explo-ration vehicle (CEV) for manned space mis-sions by 2014; and the resumption of lunarexploration. And to pay for it all, Washingtonhas promised NASA a 5% hike in funding everyyear for the next three years, with 1% annualincreases thereafter.

Significantly, fuel-cell power technology“will likely play an important role in many, ifnot all, aspects of the new Space ExplorationInitiative”, according to a paper presented atThe Fuel Cell Seminar in San Antonio, Texas, inNovember by NASA fuel-cell specialists AnitaLiang and Mark Hoberecht. Of course, NASAhas impressive credentials when it comes tofuel-cell innovation. Its scientists realized thefirst prominent applications for fuel cells for themanned space exploration programmes of the1960s and 1970s. Proton-exchange-membrane(PEM) and alkaline fuel cells were developed forthe Gemini and Apollo missions, respectively.In the 1990s, alkaline fuel cells were used on theSpace Shuttle missions, because PEM technol-ogy suffered from water-management prob-lems at the time (though PEM is once again backin favour for space applications thanks toadvances made by the automotive industry).

A big LEAP forwardLiang and Hoberecht work at NASA GlennResearch Center in Cleveland, Ohio, the focalpoint for the agency’s fuel-cell R&D work. Theaircraft fuel-cell programme, which comple-ments power-system development for space

exploration, involves about 40 NASA personneland is now consolidated under NASA’s five-yearLow Emission Alternative Power (LEAP) pro-gramme. “Our total aeronautical and spacebudget is in the order of $30–35 m per year,which does not include the funds that will berequired to integrate the technology into flightvehicles,” Liang told The Fuel Cell Review. Theagency is pursuing two distinct tracks of PEMdevelopment to meet the different needs of CEVsand exploration aerial vehicles (EAVs). The latterare remotely or robotically piloted aircraft thatcan operate for extended periods in the extremeenvironments encountered high in Earth’satmosphere (or even above other planets).

A hydrogen/oxygen PEM fuel-cell system(which will also provide drinking water for thecrew) is being developed for the CEV pro-gramme. Two US firms – Teledyne EnergySystems and ElectroChem – were selected toprovide “breadboard” prototype 5 kW PEMsystems to NASA for evaluation. In August2003, Teledyne was subsequently awarded a$4.3 m contract to deliver a 7 kW “engineeringmodel” PEM fuel-cell system. Once delivered toNASA, this unit will be tested in a thermal vac-uum chamber to simulate the extremes of tem-perature and pressure found in space.

Meanwhile, work is under way on regenera-

tive PEM fuel-cell systems (effectively,reversible fuel cells that can store energy ashydrogen and oxygen) for EAVs. The develop-ment of regenerative PEM fuel cells at NASAbegan in 1994 under the EnvironmentalResearch Aircraft and Sensing Technology(ERAST) programme. ERAST ended in 2003and a regenerative fuel cell was built and testedon the ground – but not under simulated alti-tude, pressure and temperature conditions. Inany case, the system was too heavy. “Theenergy-density requirement for high-altitude,long-endurance craft is a challenge that stillneeds to be addressed,” explained Liang. “Thiscould be improved, but we are not sure if wecan double the density to achieve the required600 Wh/kg.”

Reach for the skyBy the end of 2009, however, the EAV pro-gramme aims to develop a regenerative fuel-cell system that has been ground-tested in analtitude chamber. Phase one of the project willinvolve the building and testing of one or morebreadboards by outside contractors. Afterevaluation, NASA will then award a single con-tract to build a flight-like demonstrator system.

Meanwhile, NASA will perform technicalrisk-mitigation studies using an in-house

Aerospace applications

The US Space Exploration Initiative is likely to be an extreme proving ground for fuel-cell components and systems.

Drop the pilot: NASA’s battery-powered Helios prototype aircraft takes off from Hawaii for itsrecord-breaking flight to an altitude of 96 000 ft. A fuel-cell propulsion system was beingdeveloped for Helios before the aircraft was lost in the Pacific Ocean.

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

closed-loop regenerative PEM testbed. InNovember 2004, the agency purchased a 5 kWhydrogen/oxygen PEM fuel-cell stack fromHydrogenics, Canada, for use in the testbed.

Boyd Taylor of Hydrogenics told The Fuel CellReview that the system’s durability, low weightand ability to operate over a variety of dutycycles were key to winning the NASA contract.It also probably helped that Hydrogenics hasbeen working with NASA for a number ofyears on fuel-cell R&D. The vendor suppliedfuel-cell stacks to AeroVironment, the UScompany that developed the Helios unmannedsolar-powered aircraft for NASA.

As well as working on specific CEV and EAVprogrammes, LEAP is funding basic research.In September 2004, for example, NASAannounced that $6 m will be made available forresearch into fuel cells and associated technol-ogy for use in aircraft. This includes, but is notlimited to, primary power sources forunmanned aircraft. Such aircraft could be usedas high-altitude platforms for wireless telecom-munications systems or as remote sensing sys-tems to monitor agriculture and pollution. Asfor technical specifications, NASA says they’relikely to require a fuel-cell stack with an energydensity of about 600 Wh/kg, a 40 000 h life-cycle and the ability to run on hydrogen or con-ventional aircraft fuels.

Liang believes that fuel cells could also beused to provide electrical power on commer-cial airliners. On the ground, the fuel cell wouldbe used in place of an auxiliary power unit,which would reduce noise and cut NOx emis-sions by 20%. While in the air, the fuel cellwould provide electrical power, which in turnwould lead to greater fuel efficiency.

Just now, it appears that high-temperaturesolid-oxide fuel cells (SOFCs) are best placed tofind applications in commercial aircraft in themedium to long term. As well as running effi-ciently on hydrogen, SOFCs can use reformedkerosene jet fuel. NASA is involved in the devel-opment of both SOFCs and technology for theon-board reformation of kerosene.

Elsewhere, LEAP is working on the reduc-tion of CO2 and NOx emissions by developingsubsonic aircraft-propulsion systems that donot use hydrocarbon fuels. Liang explained:“The lowest-risk option is to run an aircraftturbine on hydrogen. This is a pretty efficientway of using hydrogen. We are currently doingsystems studies to see if there are any benefitsto making a fuel-cell-powered propeller air-craft [though] this is a preliminary study andwe don’t have any solid results. [Lookingahead] any future zero-CO2 aircraft is likely tobe a hydrogen-powered hybrid of electric-drive and turbine technologies.”Hamish Johnston

Cars and light trucks offer the best opportu-nity for the US to reduce its carbon emissions,according to a study published in theProceedings of the National Academy of Sciences(PNAS; 9 November 2004). Robert Jacksonand William Schlesinger concluded that UScarbon emissions could be reduced by 10%through the widespread adoption of hybrid-electric vehicles (HEVs), advanced dieselengines and lightweight construction. Theyalso predicted that the adoption of HEVs andother advanced technologies “could precede atransition to hydrogen vehicles”.

Jackson and Schlesinger, who are environ-mental scientists at Duke University in NorthCarolina, noted that vehicle-related carboncuts would be much easier to achieve thanattempting to sequester carbon in agriculturalsoils and plantations. Indeed, the scientists cal-culated that one-third of US croplands (44 mil-lion hectares) would need to be devoted tocarbon sequestering to achieve a similar 10%cut. This would involve much more social andeconomic upheaval than a move to HEVs, oreven the creation of a hydrogen economy.

Jackson told The Fuel Cell Review that trans-portation-related carbon cuts were “low-hang-ing fruit” and the purpose of the PNAS articlewas to highlight the fact that “transportationinfrastructure in the US provides an opportu-nity to make a serious dent in carbon emis-sions without a major upheaval to the waypeople live”. Jackson added: “The technology isthere, and we should use it before we convertan area the size of Texas to pine and eucalyp-tus. To me, it just makes more sense.”

However, Jackson was cautious in his sup-port for a move to a hydrogen economybecause, he says, it is not clear where the hydro-gen would come from. He believes that gener-ating hydrogen from petroleum would almostcertainly result in greater overall carbon emis-sions than the traditional production and useof gasoline. “Of course, [hydrogen from anysource] could be a tremendous boon to airquality in places like Los Angeles,” he added byway of qualification.

He continued: “If there is sufficient publicconcern [in the US] for carbon emissions andclimate change, there will be a debate whetherrenewable or nuclear energy is the best way togenerate hydrogen. In principle, this couldpower our vehicles and infrastructure, but weare a long way off achieving this.”

Beyond the source of the hydrogen, Jacksonsaid that questions remain regarding the envi-ronmental effects of a hydrogen economy. “Amajor environmental issue regarding hydro-gen is how much leakage occurs in the distri-bution system,” he explained. “Hydrogen is avery reactive molecule and can have significantconsequences in terms of ozone and otherchemicals in the troposphere [the lower regionof the atmosphere].” Jackson believes that leak-age could be controlled to a reasonable level,and that any negative effects would be the“lesser of two evils when compared to carbondioxide, but I can’t say that with confidence”.

A recent study by atmospheric scientists inthe UK and France concluded that “switchingto a hydrogen economy could significantlyinfluence the chemical composition of the tro-posphere”. Writing in Geophysical ResearchLetters (4 March 2004), Nicola Warwick ofCambridge University and colleagues calledfor more research to be done on the impact of ahydrogen economy on the troposphere.

According to Jackson, the PNAS articlefocused on cars and light trucks “because it issomething that people relate to and it is an areawhere rapid progress can be made”. Whileindustry and the heating and cooling of build-ings are responsible for two-thirds of US car-bon emissions, Jackson points out that thesesectors have improved their energy efficiency.“Very little progress has been made on theautomobile side,” he added. “Cars are faster andsafer, but they are not more fuel-efficient. Wehave done a terrible job as a society on thetransportation side.”Hamish Johnston

NEWS & ANALYSIS

Advanced vehicle designs are the most efficient route to lower carbon emissions.

Clean cars, clean airAtmospheric science

The ultimate driving machine?

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

NEWS & ANALYSIS

Cartridges of methanol for use in direct-methanol fuel cells (DMFCs) will be given anew classification code that will make it eas-ier for them to be transported in the cargohold of commercial aircraft. The move fol-lows a decision by the United NationsCommittee of Experts. Currently, methanolcartridges are transported as cargo on com-mercial aircraft and other modes of transportunder a general UN classification formethanol containers (UN 1230). However,many industry groups have pointed out thatfuel-cell cartridges are safer than generalmethanol containers and should therefore besubject to their own distinct set of guidelines.

The UN decision means that “consumers donot have access to the contents and the likeli-hood of leakage in transportation is [therefore]very low,” explained Brian Walsh, director ofmember services for the US Fuel Cell Council(USFCC) and staff lead for its portable powerworking group. This group has been a keyplayer in promoting international cooperationbetween the many regulatory bodies and otherorganizations affected by the issues surround-ing fuel cells on aircraft.

The UN regulations will give methanol fuelcartridges a distinct shipping name, numberand packing instruction when they are shippedas cargo, which “will help to facilitate the iden-tification of fuel-cell cartridges by internationalauthorities”, said Walsh. The classification willalso enable cartridges to be shipped separatelyfrom their micro-fuel-cell devices, so that userswill be able to carry spares with them. Today,consumer-electronic devices powered bymicro fuel cells and containing a methanol fuel-cell cartridge can be shipped as cargo desig-nated by the classification UN 3363 (DangerousGoods in Machinery or Apparatus). The newlyadopted regulation is now being sent tonational and international transportation agen-cies for implementation within their own rules.

Meanwhile, the ultimate goal of the portable-fuel-cell industry is to provide longer-lastingpower than the rechargeable batteries used inlaptop computers and mobile phones. After all,a laptop battery that lasts for two or three hoursis of limited use to somebody who wants towork throughout the duration of a 12-hourflight. Walsh believes the UN decision is a posi-tive move in that direction. “The USFCC and itsmembers continue to work [towards] gettinginternational allowance to use methanol fuel

cells and cartridges in the cabins of commercialaircraft,” he explained.

In fact, the USFCC estimates that an interna-tional agreement permitting the technologyto be taken into the cabins of commercial air-craft could be in place by early 2007, “in timeto facilitate the global commercialization ofmicro fuel cells for consumer electronicdevices”. Ultimately, though, that decision willrest with the International Civil AviationOrganization, the body that writes the regula-tions for the international airline industry andis represented by the International AirTransport Association.

For now, safety codes and standards are one of

the main priorities for pioneers of DMFCs andtheir fuel cartridges. These standards and codeswill be developed through industry organiza-tions such as Underwriters Laboratories (UL) inthe US, and the International ElectrotechnicalCommission (IEC), which is headquartered inSwitzerland (see “The importance of standards”).In the meantime, Walsh and his colleagues at theUSFCC are working with the US Department ofTransportation to establish an exemption forpassengers to carry methanol fuel-cell cartridgeson board domestic flights in the US. Similarefforts are being launched in other countries foraircraft and for other modes of transport.Siân Harris

Transportation of methanol fuel cartridges on commercial aircraft just got easier. There is still much to be done, however.

It’s better to travelPortable power

CSA America and Underwriters Laboratories(UL), two leading US standards and safety-certification groups, are to jointly develop andpublish a new standard that will set outrequirements for micro-fuel-cell powersystems and associated fuel-cell cartridges. Thestandard, entitled Handheld or Hand-Transportable Fuel Cell Power Units with FuelContainers, will be developed and proposed asan American National Standard and willcomplement work being conducted within theinternational standards community.

The project is slated for completion byDecember 2005 and will draw up specificationsfor minimum safe fuelling, design, safety-basedperformance, installation and disposal ofpackaged power systems and fuel cartridges. Aspart of the collaboration, CSA and UL will pooltheir expertise to help industry developrequirements for micro-fuel-cell powersystems and fuel containers.

Elsewhere, work is proceeding apace. Lastsummer, the International ElectrotechnicalCommission (IEC) established a new workinggroup (WG10) to draw up a standard coveringinterchangeability issues between micro fuelcells. The group will sit within IEC TC 105,which is the fuel-cell technologies technicalcommittee of the international standards body.

WG10’s objectives are to establish criteria forinterchangeability between micro-fuel-cellpower units and electrical devices, as well asbetween fuel cartridges and micro-fuel-cellpower packs. This is important because if a fuel

cartridge is connected to an incorrect fuel-cellpower unit there could be a safety problem,such as fuel leakage or an improper voltagebeing supplied to an electrical device. The sameproblems could occur if a micro-fuel-cellpower unit is connected to an incorrectelectrical device.

Micro fuel cells are expected to be longer-lasting than current rechargeable batteries andpower packs because of their higher energydensities. And because they rely on replaceableor refillable fuel cartridges, they will alsoeliminate the need for lengthy recharging times.

The importance of standards

Wireless world: internationally agreed safetycodes and standards will be key drivers in thecommercialization of micro fuel cells forportable electronic devices.

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

NEWS & ANALYSIS

Molten-carbonate fuel cells (MCFCs) will soonbe generating heat and electricity from by-products of the Japanese food industry. They’llbe doing so as part of the ambitious Super EcoTown project in Tokyo, which aims to promotea recycling-based society by inviting privatebusinesses to develop waste-treatment andrecovery processes. One such business isBioenergy, a joint venture between IchikawaKankyo Engineering, Kaname Kogyo andSan-R (a subsidiary of Mitsubishi).

Right now, Bioenergy is constructing Japan’slargest methane-gas fermentation power plantwithin Super Eco Town. The facility, which willprocess up to 110 tonnes of food waste per day,will help the food industry to meet legalrequirements to recycle or reduce food wasteby more than 20% by 2006. What’s more, themethane gas derived from the fermentationwill be fed into a MCFC power plant to gener-ate approximately 50% of the facility’s base-load electricity needs, as well as heat for thefermentation processes.

The MCFC power plant in question is a250 kW Direct FuelCell (DFC) system, whichBioenergy is purchasing from Marubeni, theAsian distribution partner for FuelCell Energy(FCE) of the US. The plant will be shipped in thesecond quarter of 2005 and is slated to be opera-tional soon afterwards. “Marubeni continues topioneer new applications for our DFC products,and this is our first power plant to operate onanaerobic digester gas from food recycling,” saidHerbert Nock, senior vice-president of market-ing and sales at FCE. Elsewhere, three of the fiveDFC plants already installed in Japan are gener-ating power from methane-based gases atwater-treatment works and breweries.

The big attraction of the DFC plant forBioenergy is its high electrical efficiency(45–50%). Because it relies on internal fuelreforming to extract hydrogen, the DFC solu-tion brings the reforming process into the fuel-cell module: flat reformer plates are placedthroughout the stack and a small amount of cat-alyst is placed in the fuel-cell passage to reformany remaining hydrocarbons. As a result,“waste” heat from the core fuel-cell process canbe recycled and put to use in promoting hydro-gen generation (see “Stationary power with adifference”, August/September 2004 p38).

“DFC power plants offer a clean and moreefficient alternative to traditional reciprocating

engine-based distributed generation,” explainedMarc Aube, vice-president for strategic businessdevelopment at Marubeni Power International.Furthermore, he believes that FCE is a logicalchoice as a partner for Marubeni. “The decisionwas based on the market we chose to focus on[commercial/industrial digester gas at powersof 50 MW or less] and which fuel-cell companydeveloped the best system for this market.”

At the moment, Marubeni acts simply as adistributor for FCE’s complete power plants,though work is under way to engage local com-panies to put the plants together. Agreementshave already been lined up with Kawasaki inJapan and POSCO in Korea, for example.“Instead of importing the whole plant,Marubeni will use our module and add its ownbalance-of-plant components such as DC-to-AC converters and fuel-processing systems,”explained Steve Eschbach, director of investorrelations at FCE.

The eventual plan is for the two companiesto create a joint venture in Asia that will pro-duce the plants locally. This will mean that onlythe fuel-cell stack modules, which are at theheart of FCE’s intellectual property, will beimported from the US. “The total weight of theplant is around 85 000 lb, of which about half isthe fuel-cell module,” said Eschbach. “If the restcould be built locally, there are considerablecost savings to be made in shipping.”

Currently, many fuel-cell purchases are sub-sidized. Bioenergy’s DFC installation, forexample, will receive funding from theJapanese Ministry of Agriculture’s BiomassNippon Strategy Programme, which has abudget of more than $200 m for food-recyclingprojects, including fuel-cell power plants.Eschbach says that in the long run, however,both FCE and Marubeni hope that cost savingsfrom technological advances and economiesof scale will make fuel-cell power generation asound commercial proposition even withoutgovernment subsidies.Siân Harris

A stationary fuel-cell system is one of thecore enabling technologies in Tokyo’sSuper Eco Town recycling initiative.

Everything’s gone greenBiofuels

Think big: Direct FuelCell power plants havebeen installed at water-treatment works andbreweries in Japan. Super Eco Town is next.

IN BRIEFAll change in stationary fuel cellsToshiba International Fuel Cells is now awholly owned Toshiba subsidiary after theJapanese parent company agreed to acquireUTC Fuel Cells’ 49% stake in the group. At thesame time, US-based UTC purchased the 10%stake that Toshiba held in its own operations.The new Toshiba business, renamed ToshibaFuel Cells Power Systems, will focus oncommercialization of polymer-electrolyte fuelcells (PEFCs) – initially for the residentialmarket, though its remit will eventuallyexpand to include industrial andtransportation markets.

Established in March 2001, Toshiba FuelCells manufactures 1 kW-class PEFCs.Headline figures include: 38% generatingefficiency (low heat value), more than 6000 h ofsuccessful operation as a generating unit, andmore than 10 000 h as a cell stack. To date, thecompany has delivered more than 40 1 kWPEFCs to the Japanese government, as well asto utilities and housing companies. Japan’sMinistry of Economy, Trade and Industry(METI) is promoting the on-site use of PEFCs asan alternative energy source for residences,and will launch a programme in 2005 tosupport the installation and monitoring ofapproximately 3000 prototype fuel-cellsystems over three years. METI forecasts thatPEFCs will generate 2200 MW of electricity forJapanese residential use by 2010.

Photovoltaics yields ‘clean’ hydrogen A solar-powered hydrogen-generation systemis now up and running at the National ResearchCouncil Institute for Fuel Cell Innovation(NRC-IFCI) in Vancouver, British Columbia.The equipment uses electricity fromphotovoltaic panels to power a HydrogenicsHyLYZER electrolyser module, whichgenerates hydrogen from water. The hydrogenwill soon be used to fuel a Ballard Nexa RMSeries fuel-cell module to provide back-uppower to the NRC-IFCI. The photovoltaicpanels, designed and installed by BritishColumbia Institute of Technology researchers,can provide up to 7 kW of energy on brightsunny days, less on rainy days and none atnight. Storing the energy as hydrogen,however, will allow users to manage the power-supply despite intermittent weather patterns.“When hydrogen comes from renewablesources, like in this particular system, webenefit from completely clean energy. Thereare no greenhouse gases; the only emissionsare oxygen and water,” said Pierre Rivard,president of Hydrogenics Corporation.

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

NEWS & ANALYSIS

Whatever the potential advantages of fuel-cellvehicles (FCVs) – and there are plenty – it’s clearthat there’s still a long road to be travelledbefore they get anywhere near the cost:per-formance of traditional vehicles based on thegasoline-fuelled internal combustion engine(ICE). Fundamental breakthroughs are neededacross all manner of enabling technologies,including hydrogen generation, on-boardhydrogen storage and auxiliary power. Eventhen, the car makers and their suppliers have ajob to do on bread-and-butter issues like thelifetime, durability and manufacturability oftheir fuel-cell components and subsystems.

It’s therefore encouraging to report thatToyota, Japan’s leading car manufacturer, issounding an upbeat note on two “new leads”

that could well fast-track its FCV programme.One of the areas singled out for attention is thecorporation’s research into carbon-basedhydrogen-storage materials, details of whichwere presented in a paper at The Fuel CellSeminar in San Antonio, Texas, in November.For some time the hydrogen-storage proper-ties of carbon nanomaterials have been thesubject of heated debate. More specifically,while significant hydrogen uptakes have beenreported by many researchers, there are big dif-ferences in the results – probably because ofvariations in the measurement methods usedand the instability of the host materials.

Toyota, for its part, has been working toobtain reproducible hydrogen-uptake data inorder to evaluate the true potential of carbonnanomaterials as a medium for hydrogen stor-age. To date, its studies have concentrated onpurified single-walled nanotubes – in this case,open-ended structures comprising a hexago-

nal network of carbon atoms that has beenrolled up to make a seamless cylinder. As forthe specifics, hydrogen-adsorption isothermsobtained at room temperature yielded anadsorption uptake of 1.3 wt% at 35 MPa. Butaccording to Satoshi Iguchi and colleaguesfrom Toyota’s technical centre in Susono, theactual amount of hydrogen stored in the car-bon pellet (including compressed gas) was2.9 wt% (or 27 kg H2/m3 of volumetric capac-

ity). Furthermore, the researchers note that thehydrogen uptake is linearly related to microp-ore volume – 0.5 ml/g in the samples studied,though 0.7 to 0.8 ml/g should be attainable ifgraphite impurities can be decreased.

In the same paper, the Toyota team revealeddetails of a new fuel-cell architecture that com-bines high power density with an intermediateoperating temperature, thereby ensuring com-patibility with on-board fuel reforming. The

Toyota’s fuel-cell specialists think thatthey might be on to something.

Innovate, accumulateVehicle development

Sabin Metal recovers platinum from fuel cell electrodes, production scrap, and process by-products.

If you produce or use fuel cells, youknow the meaning of value. We’vehelped add value for precious metalsusers for six decades. Our technicalinnovations, conservation policies, andresponsive service maximize return ofyour precious metalsvalues two ways:increased profits toyour bottom line, and

peace of mind from working with anenvironmentally responsible refiner.Now that you’re advancing fuel celltechnology, let us show you howadvanced technology precious metalrecovery and refining can add value –

and power – to yourbusiness. Tell usabout your applicationtoday.

Corporate Headquarters: 300 Pantigo Place, Suite 102 • East Hampton, NY 11937Telephone 631-329-1717 • Fax: 631-329-1985Main Plant/Sales Office: 1647 Wheatland Center Road • Scottsville, NY 14546 • Telephone 585-538-2194 • Fax: 585-538-2593Web: www.sabinmetal.com • Email: sales@sabinmetal.com Additional Facilities: Williston, ND • Cobalt, Ontario, Canada • Asia-Pacific • Latin America • Europe

Hot wheels: Toyota’s Fuel Cell Hybrid Vehicle(FCHV) is based on the popular ToyotaHighlander. The FCHV engineering team willbe keeping a close watch on the latestdevelopments in hydrogen storage and HMFCsfrom the technical centre in Susono.

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

GE Global Research, the central research orga-nization of the General Electric Company, hasbeen selected by the US Department of Energy(DOE) to head up a wide-ranging R&D pro-gramme on sustainable technologies for hyd-rogen generation. GE will contribute about$2.5 m across three separate projects, with afurther $8.5 m in funds coming from the DOEand other industry partners. The programmebreaks down as follows:● Solar electrochemical water splitting GEresearchers will team up with the CaliforniaInstitute of Technology to develop a systemthat employs solar energy to extract hydrogenfrom water using a photoelectrochemicalprocess. They aim to realize devices that meetthe DOE’s goals of 9% solar-to-hydrogen effi-ciency, a lifetime of 10 000 h and a hydrogencost of $22/kg by 2010, $5/kg by 2015 and, ulti-mately, to be cost-competitive with gasoline.● Small-scale natural-gas/bioderived liq-uid reformers Along with the University ofMinnesota and Argonne National Laboratory,GE will work on a compact reforming technol-ogy to enable hydrogen to be produced fromnatural gas and renewable fuels, such asmethanol and ethanol. “The concept wasselected as a result of detailed process analysesof more than 20 reforming concepts for appli-cation in refuelling stations,” said a GE pressstatement, adding that the emphasis is “ontechnology that can be developed and com-mercialized within a short period of time(around five years)”. ● Next-generation electrolysers Northwest-ern University, Functional Coating Technologyand GE aim to develop an electrolyser conceptthat is “efficient, affordable and environmen-tally friendly”. The goal is a reversible solid-oxide electrolysis cell capable of producinghydrogen or electricity on demand.Joe McEntee

NEWS & ANALYSIS

The US Department of Energy wantsmore emphasis on clean technologies forhydrogen production.

The generation gameResearch

essence of the new approach – called a hydro-gen-membrane fuel cell (HMFC) – is an ultra-thin proton-conductor electrolyte supportedon a solid hydrogen membrane. “A much thin-ner electrolyte can easily be realized because itis formed on a solid, non-porous membrane,”says Toyota. Another advantage is the ease ofhigh-density stacking, “because the physicalbase of the fuel cell is a metal film, not ceram-ics as in the case of SOFCs”.

To date, studies have concentrated on theperformance of single test cells. Cell prepara-tion involved the deposition of Y-dopedBaCeO3 onto a Pd film (the approximate thick-ness of the electrolyte was 2 µm). Next, theceramic cathode was screen-printed onto thecoated Pd structure, after which single cellswere operated at temperatures of 430–610 °C(with humidified hydrogen and humidifiedoxygen supplied to the anode and cathode).

Early results are encouraging. For starters,voltage versus current density plots show thatthe power density of the intermediate-temper-ature HMFC matches that of a high-tempera-ture SOFC. “At each temperature,” says thepaper, “the open-circuit voltage is as high as[the] theoretical value. This shows that theHMFC structure...works without any criticalproblems as a fuel cell.”Joe McEntee

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

Los Alamos, NM: Manufacturersof fuel-cell materials and compo-nents are set to profit from a newtechnique that enables the cost-effective fabrication of both sim-ple and complex metal-oxide films.Developed by a team at Los Ala-mos National Laboratory’s Super-conductivity Technology Center inNew Mexico, US, the polymer-assisted deposition (PAD) processcould pave the way for muchgreater commercial exploitation ofmetal-oxide films in a range of elec-trical and optical applications.

PAD uses a water-based solutionto produce a high-quality film ofnearly any metal oxide. Films canbe made from one or several met-als with controlled atomic-weightrelationships. It’s also possible tocreate amorphous, polycrystallineor epitaxial films with thicknessesof 10 nm to hundreds of nano-metres or thicker. Using PAD, thedevelopment team has made filmsof simple metal oxides (e.g. tita-nium dioxide, zinc oxide) andcomplex metal oxides (e.g. stron-tium titanate, indium tin oxide).

Metal oxides are emerging astechnically important materialsbecause of the range of physicalproperties that they possess –properties that make them attrac-

tive in applications such as fuel-cellcomponents, photovoltaic devices,gas sensors, microelectronics andcorrosion-protection devices. Upto now, however, the production

of high-quality metal-oxide filmswith the desired chemical compo-sition has not been easy (or cheap).

Metal-oxide films are typicallygrown by physical- or chemical-vapour deposition techniques thatrequire a vacuum system. Andwhile both techniques deliverhigh-quality materials, the cost ofthe deposition systems and theability to coat films only on a flatsurface have limited the applica-tions. Chemical-solution deposi-tion methods, such as sol-gel, areless costly, but many metal oxidescannot be deposited in this way.

The PAD process distinguishesitself from other coating tech-nologies by its low cost and abilityto coat large areas and irregularsurfaces, says the Los Alamosteam. What’s more, it uses 100% ofthe source materials and can con-trol the chemical phases, micro-structures and physical propertiesof the materials deposited.

Bill Tumas, director of the LosAlamos Institute for Hydrogen andFuel Cell Research, added: “Perhapsthe most promising aspect of thisnew technology is the potentialdiversity of materials that can bereadily made. PAD has the capabil-ity to enable the rapid explorationof a wide range of new materials.”

R&D FOCUSHighlights of cutting-edge research, development and innovation.

Metal-oxide films made easy

A researcher applies a few drops ofa water-based PAD solution to asilicon wafer mounted on a spin-coater. The solution contains awater-soluble polymer bound tometal ions or complexes. The spin-coater rotates the wafer at highspeed to coat it uniformly with athin layer of the solution. Then thewafer is removed from the spin-coater and heated to 150 °C toremove the water. Finally, thewafer is heated to 300–500 °C in anoxygen-rich environment toremove the polymer and oxidizethe metal left behind.

Cambridge, UK: Cambridge Con-sultants, a UK/US consultancy thatspecializes in technology transfer,has developed and tested an evap-orative cooling unit that could oneday find volume applications infuel-cell-powered laptop comput-ers and other portable electronicdevices. The unit’s design mimicsa process called transpiration inplant biology – specifically, themicroscopic openings (stomata)that plants use for water evapora-tion, providing a capillary force forthe distribution of nutrients andcooling the leaf surface.

The cooler comprises a modu-

lar arrangement of aluminium finswith etched microchannels. Thesechannels enable heat take-up andefficient fluid transfer to the evap-oration surface, while the thermalproperties of aluminium providea highly conductive link betweenthe electronic process that requirescooling and the evaporation sur-face (where heat is dissipated). Theevaporation surface uses a porousmesh membrane to ensure theeven distribution of water and alarge surface area for evaporation.

“As the processors in portablecomputers get more and moreadvanced, they require morepower and as a result they dissipateexcessive heat,” said JohannesHartick, head of Cambridge Con-sultants’ energy systems group. “If

fuel cells are to reach their poten-tial, it is essential that we overcomeobstacles to the adoption of thistechnology at an early stage.”

He added: “In testing, we see thatour evaporative cooler dissipatedthree times the amount of heatwhen compared to air coolingalone. This provides device manu-facturers with many options whenit comes to the cooling system,including the opportunity toreduce its overall size.”

During in-house evaluations,the surface temperature of theevaporative cooler was comparedwith a conventional air cooler. Thestabilized temperature of the aircooler was an unsafe 74 °C, whilethe evaporative cooler was main-tained at a much lower 47 °C.

Cooling conceptmirrors biology

Storage success:watch this spaceNewcastle and Liverpool, UK:Hydrogen storage is a big head-ache, particularly for on-boardvehicle applications, in which boththe volume and the weight of thehydrogen store are critical to thecar’s design and performance. Theplain truth of the matter is that cur-rent hydrogen-storage technolo-gies – liquefied or high-pressurehydrogen gas, metal hydrides andadsorption on porous materials –are too heavy, too bulky or toocostly for mass-market vehicles.

Now, however, scientists at theUniversity of Newcastle upon Tyneand the University of Liverpool inthe UK have reported what lookslike a significant step forward inthe quest for an energy-efficient,safe and cost-effective method forthe on-board storage of hydrogenfuel (Science 5 November 2004p1012). Put simply, they’ve devel-oped a new class of microporousmetal–organic framework (MOF)materials that allow hydrogen tobe adsorbed at high pressures butstored at lower pressures.

“Our new porous materials cancapture hydrogen gas within theirchannels, like a molecular cat-flap,”said the University of Liverpool’sMatt Rosseinsky. “After allowingthe hydrogen molecules (the ‘cat’)in, the structure closes behind it.The hydrogen is loaded into thematerials at high pressure butstored in them at much lower pres-sure – a unique behaviour.”

The current crop of MOF mater-ials are still a long way from beingpractical for on-board storage,notching up around 1wt% in thebest case versus the 6wt% mini-mum specified by US Departmentof Energy guidelines. Nevertheless,now that the researchers havedemonstrated a mechanism thatworks, they plan to go on and buildenhanced materials. Modificationsto the porous framework struc-ture, e.g. the inclusion of thermallyactivated “windows”, should allowthe desorption kinetics to beadjusted to improve the hydrogen-storage characteristics.

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

P.O Box 4217 � Antioch, CA � 94531

925-776-2407 � FAX 925-776-2406www.pdesolutions.comPDE Solutions Inc

Multi-PhysicsFinite Element Analysis

The Easy Way!With enhanced 3D capabilities, FlexPDE 4 is more than ever the

indispensible tool for scientists and engineers.FlexPDE 4 is a scripted finite element model builder for partial

differential equations. � Linear or Nonlinear � 2D or 3D plus time

or eigenvalues. � Unlimited number of variables

Pour in your equations � Pour out results

Powerful connections in wireless networks ABB Research, Switzerland, has developed a fuel-cell system that candeliver continuous power to a field device fitted with a wirelesscommunication interface (WO 2004/082051). The housing of the fielddevice contains at least one fuel cell with a membrane–electrode blockand fuel tank. The fuel cell is also fitted with an oxygen accumulatorand a water accumulator, with the latter absorbing water generatedfrom the oxidation of fuel. According to the filing, “the fuel cell formsa modular, closed system with the membrane–electrode block, fueltank, oxygen accumulator and water accumulator unit.”

Think safe, make it safe, play it safeA control unit for a vehicle-mounted fuel-cell power system will helpto ensure passenger safety in the case of a collision, according to thedevelopment team at Japanese car maker Toyota (WO 2004/103763).Put simply, the control unit monitors the likelihood of a collision. Ifthe possibility is high, the power-generation system shuts down; if acollision subsequently occurs, high-voltage relays are switched off tostop the supply of electrical power to the various loads of the vehicle.However, in the case of a collision being avoided, the fuel-cell power-generation system restarts immediately.

Desulphurization doesn’t have to be difficultA method for removing organosulphur compounds from the fuel-gasstream of a polymer-electrolyte-membrane fuel cell has been revealedby scientists at Stichting Energieonderzoek Centrum Nederland(WO 2004/099351). The principle is simple enough: the gas stream isbrought into contact with an adsorbent comprising a supportmaterial onto which metal salts have been deposited. In terms ofpreparation, the metal salt is first mixed with a liquid to form asuspension. This suspension is subsequently combined with thesupport material at 60–80 °C (with stirring and/or ultrasound waves).The product is then dried at 60–80 °C.

Lyophilic surfaces can enhance fluid flowsEntegris, US, has published details of a fuel-cell component withsurfaces that exhibit improved lyophilicity – such that liquid on thecomponent adheres closely to the surface in the form of relatively flatdroplets or sheets. According to international patent applicationWO 2004/100287, the lyophilic surfaces are formed by cold plasma orUV light treatment of the component. What’s more, the lyophilicsurfaces may be selectively provided on critical areas of thecomponent – for example, on flow-channel wall surfaces of bipolarplates and membrane–electrode assemblies – thereby inhibitingliquid blocking of the flow channels during fuel-cell operation.

Pyrotechnics yields a new take on fuellingA cartridge for pyrotechnical generation of hydrogen and a methodfor controlling the charge of a fuel cell in a portable electronic device

are detailed in internationalpatent application WO2004/092675 (revised 18November 2004). Developed by ateam at the Commissariat àl’Energie Atomique (CEA),France, the cartridge comprisessolid hydrogen-storage bodies,formed by long cords made froma pyrotechnical material thatreleases gaseous hydrogen on

combustion. The cords themselves are integrated into an inertsupport material. Furthermore, a means of ignition is arranged closeto the cord such that a combustion front runs along the cord. Thesupport can comprise channels in which the cords are arranged.

Because power is nothing without controlEngineers at UTC Fuel Cells, US, have revealed details of a fuel-mixingcontrol system for fuel-cell power plants operating on multiple fuels.According to international patent application WO 2004/062058(revised 18 November 2004), a fuel-delivery system supplieshydrogen-rich fuel to the cell-stack assembly (CSA) after controlledmixing of a primary fuel and a secondary fuel (each having arespective “equivalent hydrogen content”). The mixing of the twofuels is regulated so as to provide at least a minimum level ofhydrogen-rich fuel having an equivalent hydrogen content sufficientfor normal operation of the CSA.

Inverted cathode is better by designA common problem associated with low-temperature direct-methanol fuel cells (DMFCs) is water ingress into the diffusion layer ofthe cathode, such that oxygen can no longer be transported to thecatalyst layer of the electrode in a frictionless manner. The traditionalway to tackle this transport problem is to use a large excess of oxygen.Now, however, a team from Forschungszentrum Jülich, Germany, hascome up with a more elegant solution (WO 2004/093225). It’s a newfuel-cell design in which the diffusion layer and the catalyst layer of thecathode are inverted. The filing notes: “The diffusion layer, which isembodied in such a way as to also conduct ions, is directly adjacent tothe electrolyte membrane. The catalyst layer, oriented towards the freecathode space, can advantageously directly react with the suppliedoxygen without further transport problems.”

PATENTSThin-film processing: pump up the volumeEngineers at PEMEAS, Germany, have developed a method andapparatus for handling thin films during membrane assembly forfuel-cell electrodes (WO 2004/021485; revised 18 November 2004).Significantly, the apparatus may include automated controllers androbotic arms to facilitate high-volume processing of materials. Keyelements of the set-up include: a translatable vacuum table formounting the thin films; a perforated drum having a source ofvacuum for removing the thin films from the table; and a perforatedtransfer assembly (with a source of vacuum) to transfer the thin filmfrom the perforated drum to a target location. “When the thin filmsare provided in containers,” says the filing, “the apparatus may alsoinclude means for opening the containers to access the films.”

perforated transferassembly

perforated drum

vacuum source

thin films

movablevacuumtable

The pick of the latest international patent applications.

inert supportmaterial

ignitionsources

cords forH2 storage

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

Features and Benefits:■ Contamination-free &

leak-tight gas compression■ Discharge pressures of 3,600,

7000, 12,000, 15,000 psi and more■ Horse-power from 1 to 250 hp■ Flow rates from 0.6 to 1177 scfm■ High compression ratios■ Energy efficient

Diaphragm Compressors for Fuel Cells

www.pdcmachines.com

■ Bus filling■ Commercial and residential

vehicle filling

■ Cylinder storage■ Power generation■ Telecommunications

Applications:

Pdc Machines, Inc. • 1875 Stout Drive • Warminster, PA 18974 USA Tel. 215-443-9442 • E-mail: info@pdcmachines.com

Pdc’s clients include: Air Products & Chemicals, Inc., Air Liquide, Air Water, BOC, Cellex PowerProducts, DaimlerChrysler, Dynetek Industries, Energy Conversion Devices, Inc., FIBA Technologies, FordMotor Company, Honda, Hydrogenics, ISE Research, Nippon Sanso, Proton Energy Systems Inc., PlugPower, Quantum Technologies Worldwide, Schatz Energy Research Center, Shell Chemical Company,Stuart Energy Systems, SunLine Transit Agency, Teledyne Energy Systems, The Japan Steel Works, Ltd,Toyota, Nissan, General Motors, ChevronTexaco, EPA Testing Labs, in addition to many others...

Note from the publisherI hope that you find this fourth issue of The Fuel Cell Review informativeand enjoyable. We aim to make The Fuel Cell Review the premier source ofbusiness intelligence on R&D, technology transfer and innovation in thisdynamic industry. I have every confidence that we will deliver the highest-quality editorial, based both on the dedication of our worldwide staff and contributors, and on feedback from senior executives such as you.Should you ever have any comments to make about the magazine, or anysuggestions about how it might be improved to serve your business needsbetter, I hope you will get in touch.

And don’t forget to subscribe so that you don’t miss the next issue – February/March!

Enquiries? Please contact any one of The Fuel Cell Review team

EditorialJoe McEntee, editor Tel: +44 (0)117 930 1016 E-mail: joe.mcentee@iop.org

SubscriptionsJenny Brown, subscription and fees manager Tel: +44 (0)117 930 1034 E-mail: jenny.brown@iop.org

AdvertisingSimon Allardice, key account manager Tel: +44 (0)117 930 1284 E-mail: simon.allardice@iop.org

PublishingGeraldine Pounsford, publisherTel: +44 (0)117 930 1022 E-mail: geraldine.pounsford@iop.org

GLOBAL ALTERNATIVE FUELS 2005Exhibition and Forum8-10 March 2005Berlin Marriott Hotel, Berlin, Germany

Part of The Energy Exchange Limited

The Energy Exchange Limited is pleased to announce the Global Alternative Fuels 2005Exhibition and Forum will be held in the German capital Berlin, from 8-10 March 2005.

With transportation being the focus of the Forum, our unique speaker panel will include experts from: NEDO, IEA, ExxonMobil, US National Hydrogen Association, Total, BP, Volkswagen and Linde.

The panel will present the latest developments from Asia, Europe and the USA and cover the entire short, medium and long-term alternative fuel options and technologies available from:

Fuel Cells, Hydrogen, LPG, Bio-Fuels, Ethanol and Methanol.Join your peers and contribute ideas to this highly interactive and authoritative three-day event.

To register for the Forum or to exhibit at the Exhibition please contact:The Energy Exchange Limited • Tel: +44 (0) 207 067 1800 • Fax: +44 (0) 207 430 9513

Email: marketing@theenergyexchange.co.uk • Website: www.theenergyexchange.co.uk

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

FEATURE: RESEARCH

THE FUEL-CELL INDUSTRY, like many emerging-technology mar-kets, has witnessed its fair share of over-enthusiastic specula-tion, unrealistic expectations and, inevitably, the loss ofconfidence that follows when innovations fail to live up to theiradvance billing. Leave behind the rugged grounds of specula-tion, however, and it’s apparent that any realistic assessment ofthe commercial potential of FCs should start by answering twoquestions. First, how good must FCs be to overcome the hur-dles to commercialization? Second, how much better couldthey be made on the basis of materials science, physical under-standing and innovative engineering?

Optimists, for their part, are prone to talk of an avalanche-wise deployment of FCs and their related infrastructure –though the cost of converting the world’s carbon-based energyinfrastructure to a hydrogen economy should represent a “coldshower” to this camp.1 What they’re referring to, however, is awidely held view that the development of FCs with an accept-able price:performance will trigger the creation of a support-ing fuel-supply infrastructure. And, further, the notion that theroll-out of this infrastructure will somehow complete the cir-cle, stimulate the mass-production of FC stacks and therebyreduce their cost and attract more investment for ongoingimprovement of both FCs and fuel infrastructure.

Build the perfect FC stack and everything else will follow.That’s the essence of the argument. Trouble is, the path from lab-oratory to market for any next-generation technology is rarelyso straightforward – and FC systems, in particular, are complexentities. That complexity is hidden in the microscopic details,mostly inaccessible to the experimental “eye”. More specifically,FC operation entails circulation of protons, electrons, reactantsand water, with the processes in the structural elements of thecell coupled strongly and nonlinearly to each other.

Optimization: the role of theoryThe fundamental difficulties associated with FC design stemfrom this nonlinear coupling. Several tens of operational, trans-port, kinetic and design parameters characterize FCs, most ofthem strongly linked. A FC is like a living organism: malfunc-tioning of one organ or an unhealthy diet are likely to destroythe balance of the whole body. Or to put it another way: the FC

system must be designed as a whole, not as a collection ofstand-alone parts.

FC design can therefore be thought of as an optimizationproblem in a space of several tens of parameters, with the meritfunction being the power density obtained at given cost andlifetime. This merit function is currently the focal point for abroad technology push, with car makers, power utilities, elec-tronics companies and universities devoting millions of hours

Can theory help to improve fuel cells?MICHAEL EIKERLING, ALEXEI KORNYSHEV AND ANDREI KULIKOVSKY

A sound theoretical framework should not be seen as a time-consuming diversion, rather as the bedrock of fundamental innovation and optimization in fuel-cell materials and components.

Top: layout of PEFC with flow fields (FFs), gas-diffusion layers(GDLs), catalyst layers (CLs) and polymer-electrolytemembrane (PEM). Bottom: disciplines in FC research andvarious links provided by theory.

1. Where design meets theoryanode cathode

PEM CLCL GDLGDLFF FF

H2, fuel 02, air

+–

Fundamental understanding:structure formation andtransport in PEM and CL

Materials research:new membranes (high-T)and catalysts

Diagnostics:performance evaluation,in situ vs. ex situ

Engineering:assembling, testing,operation conditions

structure vs. function

novel tools, criteria

THEORY

advanced design?

global optimum?

and billions of dollars on experimentation, test and engineer-ing of new materials and FC systems. One thing is clear: theoryhas a pivotal role to play in all of this collective endeavour. Asound theoretical framework is the starting point from whichindustry – via subsequent experiment and field demonstration– can advance towards the ultimate endgame of mainstreamcommercial acceptance.

Figure 1 illustrates how theory links the various disciplinesin FC research. At the fundamental level, theory helps to (a)unravel complex relations between the morphology and chem-ical structure of components and their performance (frommolecular to macroscopic scales); and (b) establish diagnostictools for the characterization of those components.Understanding these relations not only facilitates the design ofmaterials, cells and stacks, it also helps to identify the causes ofnon-optimal operation.

What’s more, if process engineering is not backed up by adetailed understanding of the fundamental physics, the paybackon any investment is far from guaranteed. It is pointless to study,for example, water management in a polymer-electrolyte FC(PEFC) without appropriate models of transport and kineticprocesses in polymer-electrolyte membranes (PEMs), catalystlayers (CLs), gas-diffusion layers (GDLs) and flow fields (FFs); allof these structural elements have to cooperate well in a properlybalanced cell. Development of enhanced materials and utiliza-tion of new fuels may, in turn, dramatically affect the directionof the R&D effort, breaking bottlenecks and shifting perspectiveson transport-voltage losses, durability issues, water manage-ment, fuel supply and so on.

This review considers several examples where theory is eitherhelping researchers take steps towards the global maximum ofthe merit function or where it is adding to the culture of funda-mental understanding. The focus of the coverage is confinedexclusively to PEFCs and direct-methanol FCs (DMFCs).

PEFC components: a competitive spaceTaken together, the building blocks of the PEFC represent aspace of total competition, a space that cannot be balancedwithout a knowledge of the rules of the game. It’s thereforeworth assessing those rules in some detail, in order to figure outhow we can use this knowledge in our favour.

Let’s start with the catalyst. The CLs – the cathode side, in par-ticular – are the central organs of the FC. It is here that the fullcompetition of reactant diffusion, electron and proton migra-tion, and charge-transfer kinetics unfolds; the presence of liquidwater further complicates this interplay. Thickness, compositionand pore-space morphology steer the balance of transport andreaction. The size distributions and wetting properties of porescontrol water and heat exchange: hydrophilic micropores aregood for evaporation; hydrophobic mesopores are good for gastransport. Understanding the rules of this competition is crucialfor optimal catalyst utilization, water management and the over-all successful performance of the cell.

Another fundamental building block is the membrane.There’s an argument that “PEMs must only conduct protonsand that’s it!” In fact, there is an awful lot of competition going

on in state-of-the-art, aqueous-based PEMs. Their excellentproton conductivity is due to the cooperation of large concen-trations and high mobilities of dissociated protons.2,3 Yet thehigh acidity attacks the chemical stability of PEMs and CLs.Equally significant, water is difficult to keep in the membrane attemperatures above 90 °C, even under pressurization. The elec-tro-osmotic effect, which couples proton and water mobilities,controls water management in the whole cell. It could lead todepletion of water in the anode and flooding of the cathode,with dramatic effects on the cell performance.

Meanwhile, the major task for FFs and GDLs in a hydrogen cellis to keep them free of liquid water, since this critically impairsgaseous transport of reactants and products. For uniform con-sumption of fuel and oxygen, rates of mass transport in GDLsand FFs have to be properly balanced with reaction rates in CLs.

The membrane up closeThe membrane is a critical component of the cell, one thataffects the architecture, operating regime and voltage losses.It’s not surprising, then, that the search for high-performanceand low-cost PEMs is one of the most active areas of FCresearch. At the same time, though, the gap between the rap-idly growing data collection for all types of modified PEMs andthe theoretical understanding of structures and processeswithin these membranes is steadily growing.

The technical specification sheet for PEMs is a demandingone. They need to deliver high proton conductivity (> 0.1 S/cm),impermeability to gases, suppressed water and methanol per-meation, chemical stability and mechanical robustness. In FCvehicles, the PEM should be compatible with start-up at –40 °C,while operation at temperatures above 150 °C would signifi-cantly enhance electrode kinetics and decisively improve cata-lyst tolerance to CO. No known PEM can straddle thistemperature range, however. Most importantly, the membraneshould be inexpensive: for the automotive sector, the cost targetis $5/kW (~$35/m2), though current products are roughly 10times more expensive.

State-of-the-art PEMs like Nafion consist of fluorinated poly-mer backbones, attached pendant sidechains and sulphonicacidic groups (–SO3H) at the sidechain terminals. Less thanthree water molecules are sufficient for acid dissociation intofixed, yet flexible anions and freely mobile protons.

Upon hydration, PEMs segregate into two interpenetratingsubphases (figure 2). Polymer backbones and sidechains formhydrophobic domains. Water, mobile protons and SO3

– groupsform the hydrophilic phase; as far as this phase percolatesthrough the sample, it promotes high proton conductivity.2,3 Yetwhile these basic principles are commonly accepted, there is nounified opinion on the “details” of microphase segregation inPEMs – in spite of a large number of investigations in this area.4,5

Each proton drags some number of water molecules along.This number, called the electro-osmotic drag coefficient, liestypically in the range of 1–2. It increases with ion-exchangecapacity (IEC), defined as the molar amount of ionic groups permass of polymer material, and with the degree of hydration. Aback-flux to the anode, owing to diffusion or hydraulic perme-

RESEARCH

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

RESEARCH

ation, counterbalances the electro-osmotic flux. The resultingnet water flux depends on membrane structure and the currentdensity of PEFC operation. Overall, varying operation temper-atures and complex current distribution necessitate measuresto keep the membrane in a well hydrated state.

Early structural models, beginning with the Gierke model(inverted micelles formed by hydrated sidechains, connected byaqueous necks), considered the evolution of water pathwayswithin an inert and structureless polymer host.6,7 In contrast,recent small-angle X-ray scattering (SAXS) data from GérardGebel’s group at CEA-Grenoble, France, suggest that polymerrods and their aggregates should be considered explicitly as themembrane-forming elements.8 This opens up new perspectivesfor predictive theories of structure formation in PEMs, based ona consistent treatment of interactions between polymer, ions andwater. Despite enormous efforts across the research community,however, the theoretical understanding of structure andprocesses in Nafion is still incomplete.

Meanwhile, a large number of new synthesis routes haverecently been developed, in the main focusing on cheaper, usu-ally fluorine-free PEMs capable of sustained operation at ele-vated temperatures (T>120 °C).9 Yet, even though new PEMshave been synthesized with promising properties, none ofthem has so far succeeded in outclassing Nafion as the primarychoice for PEFCs. Put simply, the lack of a theoretical formal-ism to predict PEM performance from first principles seems tobe a real pitfall in this endeavour.

Empirical membrane research therefore imposes a dual strat-egy on theoretical membrane science. On the one hand, theunderstanding of Nafion operation is still not complete enoughto close this vast agenda of research efforts. On the other hand,theory clearly has to respond to the tremendous outreachtowards novel membranes.

Structural membrane models: status of theoryPragmatic modelling considers the membrane as a uniformmedium with effective conductivity and water-transport prop-erties. Adepts of this approach claim that they need nothingelse to integrate the membrane in modelling the overall cell per-formance. However, a structural picture of the membrane isneeded to identify root causes of membrane failure and to pro-vide new ideas about structural modifications that willenhance performance.

Most structural models of PEMs dwell on their phase-sepa-rated nature. It seems natural to start with water-filled channels(pores) as representative proton-conducting elements withinan inert polymer host. In this well defined environment, classi-cal molecular-dynamics simulations, statistical mechanics andcharge-transfer theory have been put to good use. These studiesrationalize, in an effective way, interactions of proton com-plexes and water with ionized charged groups near the surfaceof the hydrophobic skeleton. Basic modes of proton states andproton transfer in water are included, distinguishing betweentightly bound water near pore surfaces and liquid-like water inthe interior of pores. The models reveal how higher sidechaindensities and larger channel widths increase proton mobil-ity.10,11 A very practical lesson to emerge from these studies isthat longer, flexible sidechains facilitate proton conductanceand at the same time suppress methanol diffusion (in DMFCs).

Meanwhile, semiphenomenological models of membraneswelling and effective-medium percolation theory link single-pore models with the global membrane morphology.6,7 Themain additional parameter entering at this stage is the pore-space connectivity. Higher connectivity facilitates water uptakeand results in better proton conductivity. Overall, the swellingof individual pores and the formation of new connectionsbetween pores upon water uptake control the structural evo-

Structural evolution in PEMs,with chemical and physicalcharacteristics and parametersentering at each of these stepsspecified. PEM propertiesdevelop on multiple scales,ranging from molecular tomacroscopic dimensions. Thegrand challenge for theory is tolink all of these scales together.In this way, the molecular-level knowledge of, say, protontransfer and polymerchemistry can be related to thespecifications of membraneperformance.

2. PEM: from chemical architecture to morphological structure

2. Ionomer molecules1. Acid/water clustersacid strength,hydration,dissociation

3. Aggregates 4. Heterogeneous PEM

chemical architecture structural evolution macroscopic performance

hydrophobic region

hydrophilic clusters

_

_

_

__

_

_

_

_

backbone properties,length and separationof sidechains

size and shape,effective densityof acid groups

microphase separation,effective properties(transport, stability)

+

–

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

lution of the percolating network. This structural picture can consistently explain essential

experimental observations: for example, dependencies of con-ductivity on temperature, water content and IEC. For Nafion-type PEMs, the models reproduced the increase in conductivityover the complete range of relevant water contents. The dra-matic variation of the activation energy of proton transportbetween 0.1 eV for a water-saturated sample and 0.35 eV for adry sample can also be explained.12

The existence of a water-filled network of pores implies thathydraulic permeation should be considered as a mechanism ofwater transport in an operating FC, in addition to diffusion. ForNafion, there is evidence that hydraulic permeation is muchmore effective in counterbalancing electro-osmotic drag thandiffusion. Furthermore, it was found that dehydration inNafion 117 is practically irrelevant at current densities below1–2 A/cm2, while reduced thickness and larger pores improvethe internal water management. Evidently, the appropriatestructural picture has a significant impact on the water balance,not only in the PEM but also in the complete FC.13

None of the existing models, however, takes the complexinteractions in the system of polymer molecules, water andions explicitly into account. To date, all models of PEM per-formance start at some level of phenomenological description– with single pores, a network of pores or a homogeneous solu-tion. Although these models can rationalize important exper-imental findings and operational principles, they are notsufficient for predictive modelling of PEM properties.

Theory-based design: the grand challengeSo what is expected from a theory of PEM performance andproperties? For starters, we would like to understand how thechemical structure of the polymer affects the structural evolu-tion of the membrane and the mobility of protons. Havingunderstood this, we would ideally like to give some hints topolymer chemists on how best to change the “interior archi-tecture” in favour of a faster proton conduction and inhibitedtransport of solvent and reactants. Membrane propertiesdevelop on multiple scales, ranging from molecular to macro-scopic dimensions (figure 2). The grand challenge for the the-ory is to properly link all of these scales together.

For example, high proton mobility in PEMs can be under-stood only at the molecular level (steps 1 and 2 in figure 2),employing density functional theory (DFT) and ab initio molec-ular dynamics (AIMD). These quantum-mechanical calcula-tions have been used to study the kinetics and energetics of aciddissociation and proton hydration, as well as the mechanismsof proton mobility in condensed phases.2,14,15 However, theyrequire vast amounts of computer time and are, thus, limitedto small molecular clusters (~10–100 atoms), periodic struc-tures and short timescales (~10–100 ps) (step 1 in figure 2).Clearly, though, it is not sufficient to treat only the “active site”(e.g. –SO3

–) and its first solvation shell on the quantum-mechan-ical level: outer-sphere solvation makes a vital contribution toenergy changes during chemical processes. Moreover, the ener-getics of a process should be averaged over a sufficient number

of solute–solvent configurations in order to obtain meaning-ful free energies.

Within this context, a significant advance has been the devel-opment of combined quantum mechanical (ab initio)/molecularmechanics (QM(ai)/MM) approaches for practical calculationsof free-energy profiles in solutions and in proteins.16 Moreover,constrained/frozen DFT (CDFT/FDFT) methods show realpromise for advancing to step 2 in figure 2. These methods canbe adapted for studying molecular pathways of proton mobilityin representative structural elements of PEMs.

Furthermore, a better understanding of the structure anddynamics of ionomer molecules in solution is important forstudying their mutual interactions. In polymer physics, thisinformation can be used to study the formation of hydratedaggregates or bundles of ionomer molecules (step 3 in figure2). How many ionomer molecules form such a bundle? Whatare their persistence lengths? What is the density and flexibil-ity of sidechains and acid groups on their surface? Answeringthese questions will require several years of intensive theoret-ical research and experimentation on specially preparedmodel membranes.

Macroscopic membrane modelsNext, the molecular-level understanding of proton transfer insuch structures has to be advanced to the scale of macroscopicmembrane performance. Recently, a more detailed morpho-logical model of Nafion-type ionomers was suggested.5 Thismodel focuses on the question: how can one build an array ofinverted micelles if the hydrated sidechains from which theyare built are attached to the backbones arranged in bundles, andwhen the bundle persistence length is considerably larger thanthe size of the micelles? A quasicrystalline model of this

RESEARCH

Two possible types of cages in which the strings represent thebackbones or their bundles. The cages are capable of providing ashort-range-ordered system of four coordinated, invertedmicelles composed of hydrated sidechains (not shown) pointingfrom the strings towards the interior of the cages.5 Thesemicelles keep water droplets (not shown) with protons ofdissociation encapsulated inside the cage. The channels, whenthey form, bridge water droplets, through the windows in thecages. A theory of this phenomenon is under development.

3. Quasicrystalline models

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

RESEARCH

arrangement has been developed, with units cells as depictedin the cage systems illustrated in figure 3.

This model managed to rationalize the observed correlationbetween the macroscopic swelling of the membrane and the dis-tance between micelles. Channels that could be built throughthe windows in the cages will be very narrow. Upon membraneswelling, the cages expand by strings sliding along each other.At the beginning, the size of the droplets grows, but each dropletis still encapsulated within each cage, disconnected from otherdroplets. With further water uptake, the droplet ejects waterinto the windows, building small cathenoids (minimal surfaceforms) adjoining the neighbouring droplets. The analysis showsthat this process will take place as a first-order transition. At thetransition, the system may shrink slightly as some water fromthe droplets will be taken to build channels. With further wateruptake, the system will swell again, and both the droplets andcathenoids will increase in size continuously. A theory of thisphenomenon is currently under development.

So how we can use this knowledge in a practical way? This isstill not obvious, though it does seem that we at least have a bet-ter understanding of the nature of the proton-mobilitydependence on the water content. To sum up: if the channelsevolve in the beginning as extremely narrow units (less than0.5 nm radius for the narrowest part of the cathenoid) andremain narrow even in the “mature state”, it is clear why theactivation energy of the proton mobility (which is entirely con-trolled by the necks) will depend, dramatically, on the watercontent – as observed in experiments. And the more flexibleare the sidechains, the higher the proton mobility, since fluctu-ations of the chains will support the necks, reducing their sur-face tension; there could also be proton transport promoted bysidechain fluctuations.

Catalyst layers: powerhouses of the cell The realization of advanced, inexpensive catalyst materials is oneof the most pressing priorities being pursued by FC researchers.But in spite of intensive work on non-noble metal catalysts inrecent years, platinum (Pt) is still the only catalyst that providesacceptable reaction rates at operating temperatures in PEFCs(<90 ºC with Nafion, up to 200 ºC with high-temperature PEMs).Today’s CLs are highly versatile and complex. The main objec-tive is to attain the highest possible rates of desired reactions withthe minimum amount of catalyst (the US Department of Energytarget for 2010 is 0.2 g Pt/kW). This requires a huge electrochem-ically active catalyst area; small barriers to the transport of pro-tons, electrons and reactant gases; and proper handling ofproduct water and waste heat on the cathode side.

Ostensibly, CLs are rather inhospitable environments for sys-tematic theoretical treatment, an excuse used in many FC modelsto embrace simplistic approaches. Most cell and stack models –for example, those employing computational fluid dynamics –treat CLs as infinitesimally thin interfaces without structural res-olution. Conventional CLs, however, are three-phase compos-ites (figure 4). Two significant steps in their development were theadvent of highly dispersed Pt catalysts (with particle sizes in therange 1–10 nm) deposited on high-surface-area carbon, as wellas impregnation with Nafion ionomer. These advances enabledthe reduction of catalyst loadings from about 4–10 mg Pt/cm2 (inthe 1980s) to about 0.2 mg Pt/cm2.17 Most efforts in electrode the-ory and experiment focus on the cathode catalyst layer (CCL),where the sluggish oxygen-reduction reaction (ORR) incurs30–40% of the total performance losses in the cell.

There are two key measures of CL performance: catalyst uti-lization and catalyst effectiveness. The former has a straightfor-ward meaning in ideal three-phase composites: only catalyst

Figure (a): Three-phasecomposite structure ofconventional CLs. Note thehighly dispersed Pt catalyst(with particle sizes in the1–10 nm range) deposited onhigh-surface-area carbon.

Figure (b): Normalizedeffective properties as afunction of ionomer content(blue is proton conductivity;green refers to gas diffusivity;and red is exchange currentdensity).

Figure (c): Single agglomerate,indicating distinct roles ofionomer and reaction spots ofdistinct activity.

4. Catalyst layer: structure and function

PEM

ionomercarbon grains Pt nanoparticles

GDL

micropores(water-filled)

mesopores(gaseous)

10–20 µm

0.4

0.3

0.2

0.1

0.00.0 0.2 0.4 0.6

electrolyte volume fraction

50 nm

bulky ionomer(proton conductor)

ionomer molecules(binder)

non-optimalreaction spots

ideal reaction spot

optimumperformance

optimumPt utilization

(a)

(b)

(c)

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

particles at the intersections of the Pt/C phase, gas pores (con-nected with the GDL) and the ionomer phase (connected withthe membrane) can be utilized in the reaction. In real CCLs, how-ever, the concept of a “three-phase boundary” is not applicablein a strict sense (figure 4(c)) – activities of catalyst particles aremore complex functions of local composition and operationconditions. The effectiveness, meanwhile, links spatially varyingconcentrations and reaction rates with global performance.

Macrohomogeneous electrode theoryIn the early 1990s, Tom E Springer and colleagues at LosAlamos National Laboratory, US, established a one-dimen-sional (1D) macrohomogeneous model of electrode operationin PEFCs.18 Since then, other groups have adopted similarapproaches.19,20 These models could relate global performanceof CCLs to immeasurable local distributions of reactants, elec-trode potential and reaction rates. They define a penetrationdepth of the active zone and suggest an optimum range of cur-rent density and CL thickness with minimal performancelosses and highest catalyst effectiveness.

Subsequently, the macrohomogeneous theory was extendedto include concepts of percolation theory.19,21 The resultingstructure-based model correlates the performance of the CCLwith the volumetric amounts of Pt, C, ionomer and pores.Interestingly, two optimum compositions are predicted by the-ory when the ionomer content is varied (see figure 4(b)): best per-formance with ~33 vol% of ionomer, as validated by experiment,and maximum catalyst utilization with ~50 vol% of ionomer.This discrepancy is due to non-optimal gas diffusion (such thatfacilitating oxygen diffusion would bring the two optimatogether). Another striking result of the statistical theory can beseen in figure 4(b): the maximum catalyst utilization is 40%.

The theory has also been used to explore novel design ideas.As predicted by theory and recently confirmed by experiment,functionally graded layers (enhanced ionomer content near themembrane and reduced ionomer content near the GDL) raisethe performance by ~5–10% when compared with standardCCLs having uniform composition.

As the macrohomogeneous electrode theory has proven itsworth in electrode diagnostics and design, so the finer details ofCL structure and electrocatalytic mechanisms are moving intothe focus. Here, a useful concept is to consider agglomerates asstructural units of CCLs (see figure 4(c)). Ionomer moleculesinside micropores act as binder; bulky ionomer on the agglom-erate surfaces is the proton conductor. Ideal locations of catalystparticles are at the true three-phase boundary (highlighted by thered star in figure 4(c)). But how active are catalyst particles at thetwo-phase contacts (indicated by yellow stars in figure 4(c))?Models of agglomerate performance reveal that the effectivenessof catalyst utilization depends strongly on the composition andsize of agglomerates and the local operation conditions (elec-trode potential, concentrations).22 Corresponding effectivenessfactors were found to vary between 30% and 100%. It is thereforevital that micropores inside agglomerates are filled with liquidwater in order to keep Pt particles active. The theory also suggeststhat, owing to elimination of mass-transport limitations, the

effectiveness of catalyst utilization could approach 100% in ultra-thin CLs (<100 nm) consisting only of Pt/C and water-filled pores.

In spite of tremendous progress, however, there are still many“black holes” when it comes to understanding the quintessen-tial molecular processes in CLs – i.e. hydrogen/ methanol/COoxidation and oxygen reduction.23 Even for well defined andextensively studied single-crystal surfaces, the essentials of thekinetic mechanisms are not settled. Each of the key steps(adsorption, surface mobility, charge transfer and desorption)constitutes a huge scientific problem.

Moreover, recent studies have revealed drastic differencesin the kinetics at nanoparticle surfaces. Generally, small par-ticle sizes and high dispersion of Pt lead to high specific activ-ities (per total mass of Pt used). However, extremely smallparticle sizes (below ~3 nm) affect the electronic structure ofthe Pt/C system and render the catalyst surface rather hetero-geneous. This begs several questions: What is the optimumnanoparticle size? What are the best properties of nanoparti-cle arrays? Which substrate is the best?

Fortunately, theory provides various tools to facilitate researchon the fundamental aspects of electrocatalysis.23,24 DFT, molec-ular dynamics simulations and transition-state theory canunravel the pathways of elementary reaction steps. They alsohelp in terms of understanding how electrocatalytic activitiesvary with particle size and structure. At the same time, analyti-cal theories and Monte Carlo simulations resolve the complexinterplay between local processes (adsorption, desorption,charge transfer) and the surface mobility of adsorbed species. Ifconducted in tandem with the latest experimental techniques, itshould follow that more realistic paradigms of reactivity onnanoparticle surfaces will emerge. This will, in turn, enableessential kinetic parameters to be determined more reliably.24

Ultimately, the following questions should be addressed: Whatis the benefit of nanoparticles? Is it an intrinsic size effect or aneffect of surface heterogeneity? What is the role of the substrate?

The ideal layer?It can be estimated that Pt activity in conventional CLs reachesat most 10–20 % of its full potential (most of the expensive Pt isutilized ineffectively).19,21 In other words, the CLs could bemade much better and much cheaper. Despite all the compli-cations, theory does provide pointers for improvement.Composition and thickness can be readily adjusted followingrecent optimization studies.19,21 However, the task of revital-izing the ~60% unutilized Pt, not located at the active three-phase boundary, requires more innovative fabricationprocedures – i.e. site-selective electrochemical deposition ofPt at this boundary.25 Right now, it is hard to estimate howmuch effort should be invested in such procedures, but theirprospects for optimized catalyst utilization are clear.

So what does theory, as presented so far, tell us about attain-ing the ideal catalyst utilization and effectiveness? The alterna-tive to optimum three-phase composites,21 as discussedpreviously, could be to make CLs of extremely thin two-phasecomposites (~100–200 nm thick). Electroactive Pt (eventuallydeposited on a substrate) should form the electronically con-

RESEARCH

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

RESEARCH

ductive phase, with the remaining volume filled with liquidwater (as the medium for proton and reactant transport). Sincethe layer is not impregnated with ionomer, the problem of theprotonic contact resistance at the PEM:CL interface could bemitigated, making the CCL insensitive to the type of PEM. Closeto 100% of the catalyst would be utilized, since transport ofoxygen and protons would not be a problem for such thick-nesses,22 even in the absence of pores for gaseous diffusion.

As early as the mid-1980s, Mark Debe of 3M in the US starteddeveloping ultrathin nanostructured films of oriented crys-talline organic whiskers, resembling two-phase structures asdescribed above.23 The activity per total mass of Pt was foundto be about a factor of six greater than the mass activity of con-ventional three-phase CCLs – which suggests that the 3M lay-ers represent one of the most significant steps in CLdevelopment in recent years. Theory helps to explain thesupremacy of the 3M approach and suggests that this routemerits some further exploration. The existing design, forexample, does not yet exploit the potential advantages ofnanoparticles in electrocatalysis. Moreover, the fully floodedtwo-phase electrodes cannot cope properly with the problemof liquid-water removal (which is another, rather neglected,key function of CCLs). Of course, including all performancerequirements, it is not yet clear which design will be better: two-phase composite layers or conventional gas-diffusion elec-trodes comprised of three phases cleverly organized. This willrequire further systematic tests guided by theoretical estimates.

CCLs as the watershed of the cellLike living organisms, PEFCs could not function without water;equally, they literally drown in excessive amounts of liquidwater. Water is present in all essential components (see fig-

ure 1), existing in different states and participating in variouskey processes. It is pore former/filler and proton carrier in mostPEMs. Within the complex porous structures of CLs and GDLs,it exists in liquid and vapour forms. But excessive build-up ofliquid water in FFs can lock up channels and, thus, render vastparts of the FC inactive. Water is involved in various processesand reactions, including water formation in the oxygen-reduc-tion reaction (ORR) at the cathode; membrane water transportvia electro-osmosis, diffusion and hydraulic backflow; waterpermeation and diffusion in CLs, GDLs and FFs; and transfor-mation of water and heat via evaporation and condensation.

The observation of critical phenomena in current–voltageplots owing to impaired water balance has led to countlessmodels of water management in PEFCs, considering variouscomponents/mechanisms as the main elements. Yet the realityis that any model with a kinetic component and a mass-trans-port component would reproduce the critical behaviour seenin current–voltage plots. A notable exception is the CCL. It hasnever been considered explicitly as the source of any water-management problems in FCs. But is this prioritization basedon a sound assessment of the available evidence?

Invariably, PEFCs need a medium that converts hugeamounts of liquid water arriving in the CCL into vapour. A sim-ple calculation shows that only a CCL can fulfil this task. Onceliquid water arrives in GDLs or FFs, they are unable to handle it.The CCL is the PEFC’s favourite water exchanger. Incidentally,high rates of evaporation effectively convert the waste heat ofthe reaction into latent heat of vapour – like the skin regulatesour body temperature.

Effective operation of CCLs in terms of FC water balance isclosely linked to their porous structure. Ideally, local capillaryequilibrium between the liquid and gas phase should exist inthe micropores (1–10 nm). This would favour large evapora-tion rates; higher operation temperatures also help in thisrespect. At the same time, mesopores (10–40 nm) should beopen for gaseous transport of reactants and products. Relativeportions of micro- and mesopores, and their respective wet-ting properties, steer the interplay of two major functions –evaporation and gaseous transport.

A theoretical model of these processes is currently beingdeveloped. It relates measured pore-size distributions and wet-ting properties (i.e. ex situ diagnostics) to relevant effectiveproperties via detailed structural models and homogenizationmethods. The mathematical model involves transport, elec-trochemical reaction and condensation–evaporation. Overall,the solution provides the link between pore-space morphol-ogy, composition, distributed properties (concentrations, pres-sures, reaction rates, potential) and global performance.

Although not yet exploited in detail, the capabilities of thisapproach show plenty of promise. It identifies in which partsof the CCL, and at which current densities, flooding becomescritical. It reveals how problems of flooding in the FC could bemitigated by properly adjusting the CL structure and FC opera-tion conditions. And finally, it reveals under which conditionsall liquid water arriving in the CCL would leave it as watervapour through the CCL/GDL interface.

Capillary radius (radius of pores in which local liquid–gasequilibrium exists) as a function of position in the CL for variouscurrent densities. Two critical radii are indicated as dotted lines.Below lower critical radius: suboptimal wetting, diminishedeffectiveness of catalyst utilization. Above higher criticalradius: complete flooding of GDL.

5. Catalyst layer: watershed of the cell

50

100

00.0000 0.0005 0.0010

z/cm

capi

llary

radi

us/n

m

fullyflooded

optimalwetting

suboptimalwetting

0.925 A/cm2

0.856 A/cm2

0.581 A/cm2

0.083 A/cm2

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

Preliminary results for a simple variant of the model confirmthe key role of the CCL for water management in the whole cell.Figure 5 depicts capillary radii (designating the local liquid–gasequilibrium) as functions of the position in the layer for vari-ous current densities. Smaller pores are water-filled, largerpores are filled with gas. As the current density increases, localcapillary equilibrium shifts to larger pores. At the upper criticalcapillary radius, the corresponding parts of the CCL will becompletely flooded and they will fail to transport reactants.Performance will drop dramatically. Since this critical liquid-water formation occurs first in the middle of the CCL, it couldbe considered the watershed in the cell.

At this juncture, let’s revisit 3M’s nanostructured electrodes.In this instance, the solution to the problem of water removalin completely flooded two-phase electrodes would be to insertan additional layer, with a porous structure similar to conven-tional CLs though without the electrochemical functions. Inthis way, the optimization of electrocatalytic activity and goodwater management would be accomplished independently, bya spatial separation. Taken together, findings in nanoparticleelectrocatalysis along with studies of water management inCCLs suggest that the role of the porous substrate needs to beunderstood much better.

Understanding cell functionWhen considering the FC as a whole, it is necessary to join theelements discussed above into a unified model, establishing thelinks between these elements. FC models cover scales from sev-eral micrometres (CCL thickness) to a few metres (length of thefeed channels), while the processes on smaller scales are inte-grated into effective transport and kinetic coefficients.

The functional map of the conventional PEFC (figure 6) isvery inhomogeneous. In the direction normal to the cell sur-face (x-axis), this is a result of the effects discussed in the previ-ous sections. The inhomogeneity along the cell surface arisesbecause of the alternation of gas channels/landings and due tofeed consumption in the channels. Furthermore, at high cur-rents and low stoichiometries of feed flow, these inhomo-geneities play a dramatic role in the cell performance.

So what light do 2D and 3D simulations shed on all this? Oneexample is seen in figure 6, where the periodic inhomogeneitiesare due to the landing areas between FFs and the GDL, throughwhich gas cannot pass. This leads to the formation of deadzones for current generation, which have been detected inmany 2D simulations. Interestingly, dead zones form either infront of the landing areas for highly conductive GDLs, or infront of the gas channels for low-conductive GDLs.27a Based onthese findings, a new higher-performance cell design has beensuggested: a cell with so-called embedded current collectors(figure 7).27b Following on from this, a similar principle hasbeen used in the pressed-in meshed-electrode design.28

Two factors hinder propagation of 2D and 3D models, how-ever. First, simulations of 3D models in particular are very time-consuming. Generation of the map shown in figure 6 requiresabout 10 h on a multiprocessor machine. Clearly, such a tool isnot really suitable for routine comparison of experimental and

numerical curves. The second factor stems from the merits ofthe numerical approach. The big advantage of numerical mod-els is their versatility – so much so that it is difficult to resist thetemptation to take into account as many transport and kineticdetails as possible. This leads to models with several tens ofparameters, most of which are poorly known. Comparisonwith experiment is then tricky, since it is not clear whichparameters should be varied to fit the experimental data.

Nevertheless, thanks to rapid progress in computer technol-ogy, a 3D model will one day be a part of the optimization algo-rithm. To extract the maximum profit from these invaluablenumerical tools, however, it is essential to first identify keyparameters and rationalize the dependence of cell performanceon these parameters. An indispensable tool for this task is theuse of analytical models.

The models of FC performance utilize the models of CL oper-ation.29,30a Solutions to the latter problem make it possible toconstruct a simple formula for polarization voltage of a genericCL.30a Taking into account (in an effective manner) oxygentransport through the GDL, one arrives at the simplest modelof the PEFC that reproduces the shape of the experimental

RESEARCH

Functional map of the PEFC equipped on both sides with threeparallel serpentine channels.26 From top to bottom: protonconductivity of the polymer electrolyte σm(S/cm), proton currentdensity jm (mA/cm2), rate of the ORR Qc (A/cm3), oxygen (O2) andwater vapour (H2O) molar concentrations (10–6 mol/cm3) andliquid saturation S. The maps of σm and jm include both CLs and themembrane (white dashed line is the CL/membrane interface); theother maps show distributions in the CCL.

6. Mapping PEFC behaviour

O2

O2

H2O

H2O

S

S

σm

σm

jm

jm

Qc

Qc

fλj=1275 mA/cm2

inlet outlet

0.01 0.03 0.05 0.07 0.09

200 400 600 800 1000

200 600 1000 1400 1800

2 4 6 8 10 12

12 16 20 24 28

0.03 0.05 0.07 0.09y

x

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

RESEARCH

polarization curve.30b The model, however, ignores variationof oxygen concentration in the gas-supplying channels andassumes that the membrane is fully hydrated. Yet in spite of itsrather marginal practical interest, this model offers usefulinsights into cell functioning and provides a basis for con-struction of more sophisticated models.

Performance of the generic CL depends upon the availableamount of feed molecules, which in turn depends on currentdensity (owing to hindered transport of these molecules acrossthe cell). From this point of view, the DMFC is nothing but aPEFC with poor anodic reaction kinetics and crossover ofanodic fuel through the membrane. One simply has to writedown the fluxes of oxygen and methanol across the cell (includ-ing crossover) and to use the resulting expressions in the for-mulae for polarization voltage of both CLs.

The resulting model of the DMFC involves eight parameters,but the fitting of experimental polarization curves with thismodel yields a lot of useful information.31a Specially designed

algorithms enable the processing of a set of polarization curvessimultaneously to give an estimate of the basic kinetic andtransport parameters of the DMFC.31b Within the scope of thismodel, it is possible to investigate more subtle effects owing tothe potential-independent rate of methanol adsorption on thecatalyst surface.31c

The laws of fuel consumption The next step is to account for the effect of feed consumptionalong the channel. This leads to a 1D+1D model, in which therate of feed consumption in a channel is proportional to localcurrent density (with the latter dependent on local transport ofreactants across the cell). The respective model of the PEFCappears to be a very useful tool for analysis of experiments.32

Theory leads to an elegant result: if the membrane is wellhumidified, the profiles of oxygen concentration c and of localcurrent j along the cathode channel are given by simple formu-lae (see equations 1 and 2, above).32b Here, z is the coordinatealong the channel of the length L; co is oxygen concentration atthe inlet; –j is the mean current density in a cell; and λ is oxygenstoichiometry. By increasing λ, j(z) becomes more homoge-neous, thereby increasing the power density of the cell (thoughthis costs the energy for pumping). The simple laws presentedin references 32–34 help to find the optimum for the system“cell + blower” performance. Felix Buechi’s group at the PaulScherrer Institute in Villigen, Switzerland, has recentlyreported a cell with a diminishing amount of catalyst along thechannel, adjusted for running at low stoichiometry.

Meanwhile, pioneering experiments by Anthony Kucernak’sgroup at Imperial College, London, have enabled measurementnot only of the current distribution along a straight channel,but also the local current–voltage plots at different locationsalong the channel.35 Far from the inlet, the current–voltageplots revealed a negative resistance at the falling branch. Thisphenomenon has also been explained: at low stoichiometry,oxygen consumption close to the inlet rapidly increases withthe decrease in cell voltage and the remote domain suffers from“oxygen starvation”.34 A similar effect has been detected in a cellwith serpentine channels.36 Furthermore, this model hashelped to explain the effect of voltage oscillations of PEFCs inthe galvanostatic regime,37a as well as facilitating the develop-ment of a model of performance degradation.37b

Including water-management effects, one arrives at a modelthat reflects virtually all the basic processes in the PEFC.38 This

Gas-fed DMFC with embedded current collectors.27b Shown areelectron current density in the GDL and CL on the anode (ja) andthe cathode (jc) sides (mA/cm2), proton current density jm

(mA/cm2) and the rates of methanol oxidation Qa and oxygenreduction Qc (A/cm3). The maps of ja and jc include the respectiveCL and GDL; the map of jm shows the distribution in both CLsand in the membrane. White dashed lines indicate CL/GDL andCL/PEM interfaces. Note that protons move along the verticalaxis, parallel to the methanol and oxygen flow, whereaselectrons move virtually along the horizontal axis.

7. Mapping DMFC behaviour

methanol

0 500 1000 1500 2000

0 40 80 120 160 200

ja, jc

Qa, Qc, jm

ja

Qa

jm

Qc

jc

colle

ctor

colle

ctor

oxygen

colle

ctor

colle

ctor

c(z)=c0(1–λ–1)z/L

Equation 1. Oxygen concentration

j(z)/–j=[–λln(1–λ–1)](1–λ–1)z/L

Equation 2. Local current

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

model imposes an optimum on the composition and stoi-chiometry of oxygen flow, and provides an interesting optionto simultaneously fit cell polarization curves and along-the-channel profiles of local current density.

DMFC: the nature of mixed potential A model of the DMFC that accounts for methanol and oxygenconsumption in the respective channel reveals another excit-ing effect.39 It is well known that methanol crossover dramati-cally reduces the cell open-circuit voltage (mixed potential).However, the nature of this reduction is poorly understood.The list of candidates to explain mixed potential includes poi-soning of the CCL by the intermediates of methanol oxidation,CCL flooding by water produced in the methanol–oxygen reac-tion, and the loss due to the excessive flux of oxygen requiredto burn permeated methanol.

The 1D+1D model gives a new explanation of this phenome-non.39 At a small total current in the cell, a “bridge” forms nearthe channel inlet; this bridge is a narrow region where the localcurrent density remains finite as the total current vanishes. Thebridge short-circuits the DMFC electrodes, thus reducing thecell open-circuit voltage. The physics of the effect are best seenwhen the stoichiometry of methanol exceeds the oxygen sto-ichiometry. In this case, the current may occupy a finitedomain of the cell surface (figure 8); in the rest of the cell, allavailable oxygen is consumed in a parasitic reaction with thepermeated methanol. As total current in the external circuittends to zero, local current density at the channel inletremains finite (figure 8). Polarization voltages of both CLs“feel” this internal “short-circuit” and the cell open-circuitvoltage decreases. Analysis gives an exact expression for the

respective voltage loss; the numerical estimate shows that thisvalue falls into the range detected in experiments.39

Local current density in the bridge (and hence voltage loss)increases with the rate of methanol crossover. Specifically, in theabsence of crossover, the bridge does not exist. Furthermore, themodel explains the dependence of DMFC open-circuit voltageon the stoichiometry of the rate-determining flow detected inthe experiments of Qi and Kaufman.40

To sum up: there are many new options that theory can offerfor optimizing cell performance – too many options to be con-sidered in a review of this length. Based on a number of simpli-fying but realistic assumptions, analytical models of PEFCs andDMFCs yield valuable understanding for rapid, reliable cellcharacterization. Furthermore, these models can be used aslow-level counterparts of more sophisticated 2D and 3Dnumerical models, providing a bridge between experiment andheavyweight, many-parameter CFD models.

Finding your way in white waterWithin the complex network of disciplines involved in FCR&D, two major streamlines exist at the extremes. One type ofstudy focuses on enhanced design of materials, membranesand CLs. In this respect, highly resolved structural models andreliable ex situ diagnostics are needed to help scientists correlatestructures with transport and kinetic processes – and to ensurethey are not guided by trial-and-error alone. The otherapproach focuses on performance modelling at the systemslevel: how do we build the best FC with existing components?These “black box” approaches provide information on in situperformance, but they also help us to envisage how changes tothe chemical architecture of key materials could affect FC per-formance. Of course, it is crucial to integrate both types ofapproach to provide a coherent theoretical framework of FCcomponents and systems.

In a recent article in Nature,41 the Nobel prize-winning physi-cist Steven Weinberg encourages researchers to go to the roughwater: “My advice is to go for the messes – that’s where theaction is.” In the case of FCs, that means things like our incom-plete understanding of membrane structure and operation,unsatisfactory catalyst utilization and non-optimal cell design.And yet this “mess” underpins another stimulating messagethat should resonate beyond the confines of the research labo-ratory: FCs can be made much better.

Further readingThe reference list for this feature article can be found in theonline version at fcr.iop.org.

Michael Eikerling is assistant professor in the Department of Chemistry,Simon Fraser University, Burnaby, British Columbia, Canada, with asecondment to the Institute for Fuel Cell Innovation, National ResearchCouncil, Vancouver, British Columbia. Alexei Kornyshev is professor ofchemical physics in the Department of Chemistry, Faculty of PhysicalSciences, Imperial College, London, UK. Andrei Kulikovsky is seniorresearcher in the Institute for Materials and Processes in Energy Systems(IWV 3) of the Research Center Jülich, Germany.

RESEARCH

The profiles of local current density in a DMFC along themethanol channel for indicated values of dimensionless totalcurrent in the cell.39 As the latter tends to zero, the local currentdensity near the inlet remains finite.

8. Along-the-channel current distribution

0.15

dim

ensi

onle

ss c

urre

nt d

ensi

ty

0.10

0.05

00 0.2 0.4 0.6 0.8 1.0

0.010 0.025 0.050 0.075

z/L

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

FEATURE: INVESTMENT

IF THE MUCH-HYPED hydrogen economy eventually comes topass, gasoline will be replaced by hydrogen as the primary fuelfor vehicles. That’s likely to be good news for a number of rea-sons, not least that it will reduce US dependence on foreign oil,owing to the fact that hydrogen can be generated from a diverserange of energy sources such as natural gas, coal, nuclear andwind. Yet if hydrogen is to become more environmentallyfriendly, sustainable and reliable than gasoline, significantimprovements must be made to the technologies employed forthe production, distribution and use of the fuel.

The overall cost, energy inputs and greenhouse-gas (GHG)emissions of a hydrogen pathway depend on the primaryenergy source (feedstock), production technology and deliverymode used. All of these parameters will change over time as theenabling technologies mature. What’s more, all hydrogen path-ways will require significant investment in infrastructure, suchas generation and distribution systems and fuelling stations.

Right now, steam reformation (SR) of natural gas (NG) is themost common hydrogen-production method – though natu-ral gas is becoming more expensive and scarce in the US andmany other developed countries. On the up side, hydrogen canalso be made from domestic and CO2-neutral feedstocks,including biomass and the electrolysis of water (the last of whichcan make use of electricity from nuclear or renewable sources).Hydrogen production also lends itself to the capture of CO2,with underground storage or sequestration allowing domesticcoal to be used as a feedstock with limited GHG impact.

Enabling technologiesHydrogen can be used in vehicles powered by either modifiedinternal combustion engines (ICEs) or fuel cells. A number ofstudies conducted on behalf of governments, energy compa-nies and car makers have concluded that hydrogen fuel-celltechnologies of the future could achieve a fuel economy that istwo to three times better than that of today’s gasoline ICE vehi-cles. Furthermore, our ongoing studies here at TIAX and dis-cussions with car makers indicate that hydrogen ICE vehiclescould achieve 20–40% improvement on fuel economy withoutsignificant modifications to the vehicle (i.e. by means of weight

reduction and engine hybridization). Clearly, though, new technologies for safe, efficient, compact

and cost-effective storage and delivery of hydrogen are going tobe crucial to the hydrogen economy. Compressed gaseoushydrogen (cH2) and liquid hydrogen (LH2) are the two most com-mon storage and delivery methods today. However, in the longterm, cH2 and LH2 may be too expensive, inefficient (LH2 only),and bulky for storage and delivery of hydrogen as a transporta-tion fuel. As a result, the US Department of Energy (DOE) hasissued a “Grand Challenge” to develop advanced hydrogen-stor-age options for both vehicular and stationary applications (see“Hydrogen storage: the grand challenge”, June/July 2004 p17).

All current hydrogen pathways based on cH2 or LH2 use more

Hydrogen infrastructure:why, when, how much?

STEPHEN LASHER AND STEFAN UNNASCH

The creation of national and international hydrogen-fuelling infrastructures will require decades of investment and technological innovation. The latest studies from the US shed light on the commercial

challenges – and opportunities – associated with hydrogen generation, distribution and storage.

Pay and go: all hydrogen pathways will require significantinvestment in fuelling infrastructure. The risk will be borne byboth the fuel providers and vehicle manufacturers, and will bepassed on to consumers and/or tax-payers.

AIR

PR

OD

UC

TS

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

energy and emit more GHGs than gasoline production anddelivery (figure 1). Electrolysis powered by a typical US elec-tricity grid is the most energy- and GHG-intensive optionshown in figure 1, though operators of electrolysis systemscould take steps to ensure that electricity comes from renew-able sources. However, renewable energy currently accountsfor less than 10% of US electricity production. Clearly, newpolicies and/or additional technological breakthroughs will berequired before renewable energy could become the primarysource of hydrogen production in the US.

The least energy-intensive pathway is centralized hydrogenproduction via SR of natural gas combined with hydrogenpipeline delivery. Due to the large scale, however, this option willonly be economical for most fuelling stations when there aresufficient numbers of hydrogen vehicles on the road (i.e. morethan 30% of on-road vehicles in a typical large city are hydro-gen-powered). On-site SR of natural gas at the fuelling stationinvolves similar primary energy use and GHG emissions as cen-tralized production. This pathway can be practical when thereare relatively few hydrogen vehicles on the road because thefuelling stations can effectively serve as few as 10 vehicles perday. However, the high-efficiency, small-scale, low-cost imple-mentation of this technology has yet to be demonstrated.

One thing is clear: all hydrogen pathways will be expensive.Hydrogen is expected to cost two to three times more thangasoline on a per-unit-energy basis, assuming an average USpre-tax gasoline price of $1.25/gallon (figure 2). For centralizedproduction, the higher cost is related to transporting the hydro-gen, while on-site production is expensive owing to the highcost of natural gas or electricity.

Despite being inferior to gasoline on an energy basis, if ahydrogen vehicle can achieve much higher fuel economy than

its gasoline counterpart, its overall (i.e. well-to-wheel) energyuse, GHG emissions and cost can be lower. At least 30% betterfuel economy is needed for hydrogen production from naturalgas to result in lower GHG emissions, and at least equivalent pri-mary energy use compared to gasoline. Note that there wouldalso be a complete reduction in petroleum-based energy use in

INVESTMENT

Left: primary energy use for gasoline and various hydrogen pathways. Gasoline is currently the most energy-efficient fuel pathway;all hydrogen pathways use at least 30% more primary energy. Right: GHG emissions for gasoline and various hydrogen pathways.

1. Energy use and emissions

gasoline

cH2, NG (central SR,pipeline delivery)

cH2, NG (on-site SR)

543210

cH2, NG (central SR,LH2 delivery)

cH2, grid power(on-site electrolyser)

energy (MJ/MJ)

Notes• energy LHV basis• primary energy input/fuel delivered• NG = natural gas

fuel in tankpetroleumother fossil fuelnon-fossil fuel

500 100 150 200 250 300 350

GHG emissions (g/MJ)

GHG from fuelGHG from fuel chain

Greenhouse-gas (GHG)emissions weighted byglobal-warming potential

renewable power

Projected pre-tax fuel costs for gasoline and various hydrogenpathways reveal that hydrogen is a relatively expensive fuel(typically two to three times more expensive than gasoline).Hydrogen vehicles will need to show significant improvements infuel economy to achieve fuel-cost benefits over gasoline vehicles.

2. Counting the cost

cH2, NG (centralSR, pipeline

delivery)

gasoline

cH2, NG(on-site SR)

cH2, NG (centralSR, LH2 delivery)

cH2, grid power(on-site

electrolyser)

0 1 2 3 4 5 6fuel price, ex-tax ($ per gallon gasoline equivalent)

long-term projections

tax

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

INVESTMENT

most cases and, ultimately, the elimination of dependence onimported oil. If a hydrogen vehicle can achieve two to three timesbetter fuel economy, at least three hydrogen pathways – central-ized SR with pipeline, LH2 delivery by tanker truck and on-siteSR – become attractive on a fuel cost per mile basis. Electrolysispathways, although expensive in this scenario, might be attrac-

tive when coupled with new wind-power projects.In fact, the success of a hydrogen economy will depend to a

large extent upon hydrogen vehicles achieving fuel economiesthat are superior to those of their gasoline-powered counter-parts. Here at TIAX, our studies have projected fuel economiesfor hydrogen vehicles based on powertrain improvementsalone. Compared to a state-of-the-art gasoline-powered ICEV,a hydrogen ICEV is projected to offer a 20–40% improvementin fuel economy; a hydrogen-fuel-cell vehicle (FCV) of thefuture is projected to offer a 2.5–2.7 times improvement in fueleconomy compared to the gasoline ICEV. These results (takenfrom our previous study and ongoing work for the DOE) areconsistent with modelling done by Argonne NationalLaboratory, US, vehicle manufacturers and others.

Consequently, if hydrogen vehicles are competing with con-ventional vehicles, both hydrogen ICEVs and FCVs could pro-vide overall GHG-emission reduction and more efficientenergy use, though only FCVs could provide fuel-cost benefits.On the other hand, when hydrogen vehicles are compared tosimilar gasoline or diesel-powered hybrid-electric vehicles(HEVs) that are projected to have 10–40% better fuel economythan conventional gasoline vehicles, only FCVs could poten-tially come out on top in all categories.

Risks and the risk-takersAnother critical consideration is the cost and financial risk ofinstalling a new transportation fuel infrastructure. The hydro-gen fuel costs discussed above assume that a large demand forhydrogen will result in economies of scale in production anddelivery. During the transition period, however, capital costswill be high and equipment utilization will be low – because theinfrastructure must be in place before significant numbers of

A slow transition to a hydrogen economy poses a huge financial risk to infrastructure stakeholders (left), while a rapid transitionyields a much more favourable outcome (right). The latter assumes 100% market penetration of H2 vehicles in 60 years.

3. Transition is everything$350

$300

$250

$200

$150

$100

$50

$0

($50)2003 2013 2023 2033 2043 2053 2063

50%

60%

70%

40%

30%

20%

10%

0%

–10%

infrastructurecash flow

infrastructurecapital investment

H2 vehicles as% of all LDVs

year

cum

ulat

ive

dolla

rs (b

n)

% o

n-ro

ad L

DVs

In the long term, the generation of hydrogen from natural gascould lead to a greater than 50% reduction in vehicle GHGemissions. Factor in hydrogen generation from renewableresources and it could be possible to eliminate vehicle GHGemissions over the same time frame.

4. Cleaning up their act1800

1600

1400

1200

1000

800

600

400

200

02010 2020 2030 2040 2050 2060

with no hydrogen vehicles

GHG

emis

sion

s (m

illio

n to

nnes

per

yea

r)

renewable-based H2

gasoline ICEVsH2 vehicles

year

% o

n-ro

ad L

DVs

$500

$400

$300

$200

$100

$0

($100)2003 2013 2023 2033 2043 2053 2063

year

100%

80%

60%

40%

20%

0%

–20%

infrastructurecash flow

infrastructurecapital investment

H2 vehicles as% of all LDVs

cum

ulat

ive

dolla

rs (b

n)

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

hydrogen vehicles can be sold. At this early stage in the roll-out,the installation of hydrogen fuelling stations will be dictated bythe need to provide hydrogen fuelling coverage, rather than byvehicle demand and production capacity.

TIAX has developed a model of the transition to a hydrogeneconomy that evaluates the financial risks and the effects thatpotential triggers may have on various hydrogen-infrastruc-ture stakeholders. The model considers the “time-value ofmoney” so that early investments are weighted more heavilythan future profits. The model also permits the user to projectthe build-up of a hydrogen infrastructure over time based on anumber of input parameters, including a hypothetical hydro-gen-vehicle market-penetration curve.

Model results for cumulative infrastructure cash flow andcapital investment show that a slow transition to a hydrogeneconomy represents a huge risk to infrastructure stakeholders.In this conservative scenario, in which hydrogen vehiclesaccount for only 38% of all vehicles in 60 years, a period of 40years and a $50 bn investment is required before simple paybackis achieved (figure 3, left). The recovery of early investment takeseven longer – 50 or more years based on our discounted cash-flow analysis. All of these results assume that hydrogen is pricedto provide fuel-cost parity with gasoline ICEVs on a per-milebasis. A rapid-transition scenario (figure 3, right), in whichhydrogen vehicles achieve 100% market penetration in 60 years,yields a much more positive result. But although this model cutsthe cash flow and break-even capital investment forecast in half,to about 20 years and $25 bn, the question remains as to whetherhydrogen vehicles, car and equipment manufacturers, andindeed the public, will be ready for such a rapid transition.

The results in figure 3 were obtained by assuming that thegasoline-vehicle fuel economy improves from today’s fleetaverage of 21 mpg to 30 mpg (perhaps due to hybridizationand/or other powertrain improvements) in 60 years, and thatthe hydrogen-vehicle fuel economy improves from 42 mpeg to75 mpeg (2–2.5 times better than gasoline vehicles) over thesame period. We have further assumed a 100% road tax “holi-day” for hydrogen in the early years and then gradually phasedthis out as hydrogen becomes a more significant fraction oftotal vehicle-fuel consumption.

This preliminary analysis emphasizes the importance of con-tinued R&D and the need for innovative solutions – for exam-ple, the regional build-up of fuelling infrastructure and the useof mobile fuelling stations in the early years of the transition.Although more optimistic scenarios are possible, early hydro-gen sales are likely to require some subsidization to be compet-itive with conventional fuels. Outside the US, in countrieswhere gasoline is taxed more heavily, cash flow for the hydro-gen infrastructure stakeholders will be improved, but hydro-gen will eventually have to compete on a fully taxed basis unlessother tax revenues can be substituted.

It’s worth noting that our results are based on projections ofthe future cost of a highly efficient hydrogen infrastructure. Wedid not use federal or industry cost and performance targets,and there is ongoing work at the DOE and elsewhere to improvethe key metrics beyond those projected here.

Meanwhile, preliminary results on primary energy use andGHG emissions show that hydrogen generated from natural gascan reduce automotive GHG emissions by about 50%, althoughsignificant GHG reductions are not realized for about 25 years.These cuts depend on the assumed vehicle fuel economies, thetiming of hydrogen-vehicle introduction and the mix of hydro-gen-supply options. A more realistic scenario, however, is onein which hydrogen is made from a variety of domestic energysources, including natural gas, coal, biomass and renewablepower (such as wind) – especially as US natural-gas consump-tion is forecast to rise by 1.5% through 2025, with domestic pro-duction increasing by just 0.6% over the same time period.

The results in figure 4 were obtained by assuming the samefuel economy improvements and hydrogen-supply mix as infigure 3 and hydrogen-vehicle introduction consistent with therapid-transition scenario. More aggressive improvements inboth gasoline- and hydrogen-vehicle fuel economy combinedwith hydrogen from non-carbon sources could yield furthersubstantial reductions in GHG emissions. As figure 4 shows,producing hydrogen solely from renewable-energy sourceswould eliminate vehicle GHG emissions in 60 years, assuming100% market penetration of hydrogen vehicles.

Up to the challenge?To sum up: the performance and fuel cost of hydrogen vehicleson a per-mile basis can be superior to that of conventional gaso-line vehicles – provided that the appropriate hydrogen pathwayis chosen and hydrogen vehicles achieve superior fuel economy(twice-as-good fuel economy may be required). That said, it’sclear that hydrogen vehicles face a number of challenges,including the investment risk associated with implementing afuel-supply infrastructure and uncertainties surrounding vehi-cle cost and performance. Hydrogen vehicles must offer supe-rior fuel economy, competitive vehicle cost and other benefitsthat consumers find compelling – the unique design of the GMHywire FCV is a good example. Additional advantages mayinclude reduced maintenance and cost (for example, no oilchanges) and quiet operation.

Hydrogen vehicles will also face significant competitionfrom advanced gasoline and diesel ICE vehicles that are cleanerand more efficient than conventional gasoline vehicles, includ-ing ICE–battery hybrids (although hydrogen vehicles can alsobenefit from hybridization). In addition, the fact that signifi-cant GHG reductions are unlikely to be realized for the first 25or more years of transition highlights the need for other vehi-cle and fuel technologies, such as gasoline or diesel HEVs orplug-in HEVs, to improve the situation in the foreseeablefuture. Despite the current uncertainties and challenges, oneenduring benefit of the hydrogen economy will be the moveaway from dependence on imported oil and towards diverse,domestic and possibly renewable energy sources.

Stephen Lasher is an associate principal and manager of the Hydrogen andFuel Cells Unit at TIAX LLC, a collaborative R&D company headquartered inCambridge, Massachusetts, US. Stefan Unnasch is a principal at TIAX LLC.E-mail: lasher.stephen@TIAXLLC.com.

INVESTMENT

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

TECHNOLOGYTRACKING

Also in this section

30 MEAs just got more durable

31 Precious-metals recycling

32 Fuel cells and locomotives

33 A different take on DMFCs

Nanomaterials, big opportunities

In any debate about emerging technologies thatcould turbocharge the commercial prospectsof fuel cells, there’s a better-than-evens chancethat carbon nanotubes will figure prominently.These unique nanostructures boast someremarkable properties. For starters, they arevery strong: their tensile strength is 50–100 GPaand their modulus is 1 TPa (i.e. almost 50 to 100times stronger than steel, but at one-sixth of itsweight). Second, they are excellent electricalconductors. Indeed, they are theoretically farsuperior to copper if they are aligned along theiraxes: just 0.005% weight loading of nanotubesin epoxy resin can confer electrostatic proper-ties to this insulating material. They also havethe useful property of being excellent heat con-ductors along their axes and great insulatorsperpendicular to their axes. In addition, theirstructure allows other molecules to be sup-ported on or in the tube in a much more con-trolled way than is possible using bulk materialssuch as graphite.

With a feature set like this, it’s no wonderthat fuel-cell companies are taking a seriouslook at carbon nanotubes as a means toenhance the performance of their compo-nents. It’s early days but a cursory evaluation ofthe papers presented at the industry’s maintechnical conferences shows that carbon nan-otubes are now being touted for applications incatalyst supports, gas-diffusion layers, bipolarplates and even as hydrogen-storage materialsfor fuel-cell vehicles.

There’s just one snag: carbon nanotubes arestill a relative newcomer in the world ofadvanced materials, so it is difficult to secureconsistent, high-quality samples in significantvolumes. And although R&D groups do notneed mass-production quantities, or indeedmass-production prices, they do need to knowthat the purity of their raw material is guaran-teed, and that the specifications of the materialwill be the same when purchased in six or 12months’ time.

One company looking to capitalize on thisgap in the supply chain is Thomas Swan, a UK-based manufacturer of speciality chemicals.Its strategy is simple enough: in contrast to

the university spin-outs that have used theircarbon-nanotube expertise to develop spe-cialist products, Thomas Swan considers car-bon nanotubes to be a raw material that needsto be manufactured and sold, just like any ofits other chemicals. The company’s manufac-turing process was developed in collabora-tion with the department of materials scienceand the department of chemistry at theUniversity of Cambridge, an institution thatit has worked with for the past four years. Theuniversity owns the patents to the process,but does not have the manufacturing infra-structure and experience to commercialize it.In exchange for exclusive rights to use thesepatents, Thomas Swan makes a royalty pay-ment to the university.

Nanotubes and how to make themAn ideal nanotube can be thought of as a hexag-onal network of carbon atoms that has beenrolled up to make a seamless cylinder. Just ananometre across, the cylinder can be tens ofmicrons long, and each end is “capped” with halfof a fullerene molecule. Single-wall nanotubescan be thought of as the fundamental cylindri-cal structure, and these form the building blocksof both multiwall nanotubes and the orderedarrays of single-wall nanotubes called “ropes”.

Thomas Swan’s manufacturing process isbased on chemical-vapour deposition. In out-line, a hydrocarbon feedstock passes into a hotfurnace and nanotubes grow on a magnesium-supported iron catalyst. This structure is thenwashed in an acid bath, to remove the catalystand substrate, and the resulting slurry is neu-tralized to yield the final product. The tech-nique can be used to make both single-walledand multiwalled nanotubes and is now provid-ing consistent evaluation quantities from apurpose-built plant in Consett, north-eastEngland. The facility, which came online inApril 2004, is designed with scale-up in mind –production levels can be doubled within sixmonths if the demand is there, according toHarry Swan, business manager for the carbon-nanomaterials business.

The company claims that its nanotubes are

Advanced materials

Carbon nanotubes are touted as the next big thing by materials scientists. But what are they? And what can they do for fuel cells?

The producers: Thomas Swan’s dedicatednanotube facility (top) came onstream in April2004. The company now sells commercialquantities of carbon nanotubes under theElicarb trademark and is keen to developstrategic collaborations in the fuel-cell market.Centre, bottom: computer models of single-walled and multiwalled carbon nanotubes.

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

already 90% pure, which means that 90% of thematerial is single-walled nanotubes (ratherthan multiwalled nanotubes, amorphous car-bon or residual catalyst and catalyst supportfrom the manufacturing process). “We cantypically manufacture 2 kg of high-purity sin-gle-walled tubes per month,” said Swan. “Wehaven’t started selling multi-walled tubes yet,but plan to do so. We started with single-walledbecause they are harder to make, but we realizethat multiwalled tubes are also potentiallyimportant for applications such as fuel cells.”

The nanotubes are currently sold in theform of a dry powder, though they will soonbe available in a slurry. “A big technical effortis going into how to disperse and stabilizenanotubes with the addition, for example, ofsurfactants,” said Swan. “We are not going tostart making composites with our material,but could create dispersions in a customer’sresin if requested. We are keen to deliver thematerials in a usable form.”

Meanwhile, the R&D collaboration betweenThomas Swan and the University of Cambridgecontinues to pursue new opportunities. Swansays the university laboratories are developingan advanced production technique based on

nanotube formation in the vapour phase. Theirapproach involves the formation of nanotubesfrom a vaporized catalyst that produces a“sock” of material in the furnace. This materialcan then be directly and continuously “wound”out of the furnace onto a spool to yield a nano-

tube-fibre staple. If the process can make theleap to the factory floor, it will require smallerquantities of iron catalyst and no substrate – apotential route to much purer carbon nano-tubes in truly bulk quantities. Siân Harris

TECHNOLOGY TRACKING

Partnership is a key element of Thomas Swan’scarbon-nanomaterials business. Such a strategyis mandatory in a market like fuel cells, where themain applications for carbon nanotubes are stillto be defined. To fast-track his division’s accessinto fuel-cell companies, Harry Swanapproached Core Technology Venture Services,a UK/German consultancy and venture-capitalfirm that lists fuel cells as a core competency.

So far, the response from component makershas been encouraging. “Everybody we spoke towas interested; we didn’t have to sell it,” said PhilDoran, a partner at Core Technology. Andalthough carbon nanotubes are still expensive,he says that this is not a big problem if they can beshown to significantly enhance performance

and/or reduce the need for expensive platinum-group catalysts. “The benefits spread throughthe system,” he added. “They [the componentmakers] are finding the results of early researchgood enough to say ‘carry on’.”

While the partnership with CoreTechnology has opened doors to potentialcustomers, Swan is keen to emphasize that hisbusiness group ultimately sees itself simply as amaterials supplier. “Nanotubes are rawmaterials that will go into components,” hesaid. “We are not asking for IP and royaltyconstraints downstream like somenanomaterials companies. Why would youwant to buy something if the raw-materialmanufacturer put constraints on the sales?”

A foot in the door

Researchers at 3M in the US have come up witha way to enhance the durability of the gas-dif-fusion layer within the company’s mem-brane–electrode assemblies (MEAs). The MEAconsists of the polymer-electrolyte membraneitself, the anode and cathode electrode layersand the gas-diffusion layer (GDL). The GDL isa porous element that, with the help of ahydrophobic coating, helps to manage watermovement around the fuel cell.

In a traditional MEA, the GDL loseshydrophobicity over time, which in turndegrades the cell’s efficiency. To get round thisproblem, 3M is in the process of patenting a newcoating that retains those hydrophobic proper-ties more readily. The development team, whichhas also improved the porous material, addedsome quantitative substance to its argument bycomparing the durability of MEAs based on thenew GDL with previous products.

When subjected to aging tests, MEAs withthe old GDL suffered a substantial reduction inthe limiting current density after just a fewhundred hours. In contrast, the new GDL didnot show any substantial differences in limit-

ing current density after accelerated aging forup to 2016 h. Similarly, the new GDL was moreresistant to chemical oxidation when theMEAs were immersed in a bath of hydrogenperoxide; corrosion current densities werefound to be two to three orders of magnitudelower than the existing GDLs.

Encouraging though the results may be, thedurability of the GDLs in fuel-cell systems willdepend to a large extent on the overall systemengineering and operating conditions. “TheMEA is just one part of the puzzle... there haveto be system improvements too,” explainedMichael Lynn, manager of commercializationservices at 3M, adding that feedback from cus-tomers who have already evaluated the newMEAs reinforces 3M’s in-house test results.

These early customers are now integratingand certifying the new MEAs in their systems.3M anticipates that products based on theenhanced GDL will emerge towards the middleor end of 2005. Target markets include long-lifetime applications such as distributed gener-ation and transportation.

Lynn says that the materials and equipmentcosts of the new GDL are the same as for theprevious generation of materials. However, theefficiency of the manufacturing process hasbeen improved because the new GDL is fabri-cated on a flexible roll substrate that can thenbe cut to size and shape. 3M is also working onenhanced membrane and electrode layers,which it hopes to introduce into its MEAs overthe next year. ●

Aging gracefullyInnovative coating chemistry is the keyto an enhanced gas-diffusion layer formembrane–electrode assemblies.

current density (mA/cm2)

control, 0h72h120h264h

cell

volta

ge (V

)

aging time increases

0 400 800 1200 1600

0.8

0.6

0.4

0.2

0

current density (mA/cm2)

cell

volta

ge (V

)

0 400 800 1200 1600

0.8

0.6

0.4

0.2

0

no substantialchange seen

control, 0h504h1008h1502h2016h

Development scientists at 3M assembled MEAs with aged GDLs on the cathode. The new GDL(left) did not show any substantial differences in limiting current density after accelerated agingfor up to 2016 h; the old GDL (right) suffered a substantial reduction after a few hundred hours.

Components

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

TECHNOLOGY TRACKING

Precious metals play a fundamental enablingrole in low-temperature fuel cells. Platinum isa firm favourite for catalysing the anode andcathode reactions in the membrane–electrodeassembly (MEA), though ruthenium is com-monly used where exposure to carbonmonoxide is anticipated. Elsewhere, otherplatinum-group metals like rhodium and pal-ladium play their part in the fuel-reformingand purification process.

Yet while the properties of these metalsmake them invaluable in fuel-cell systems,their usefulness comes with a hefty price tag.With only about 5 g of precious metal in everytonne of ore mined, the economic and envi-ronmental costs of extraction are enormous.On the back of this, variations in supply anddemand can trigger significant fluctuations inmarket prices – to such an extent that theresulting volatility could pose a significantentry barrier to the fuel-cell industry if nothandled properly.

The answer, according to the internationalmetals and materials group Umicore, is to pur-sue a well-thought-out strategy with respect toprecious-metals management and recycling.With established operations in Belgium andGermany, Umicore is a mainstream supplier ofMEAs to companies right across the fuel-cellindustry, though it does not see its role as end-ing with the initial component supply.

As well as advising customers on the buyingand selling of newly mined precious metals, forexample, Umicore’s core competenciesinclude the recycling of end-of-life compo-nents – common practice in the chemical andautomotive industries, but only now startingto be taken seriously in the emerging fuel-cellsector. “Very few fuel cell companies consid-ered precious-metal recycling five years ago,but it is becoming important now,” said KnutFehl, Umicore’s manager for applied technol-ogy fuel cells for North America. “We are help-ing to educate the market.”

The right chemistryThe typical process for recycling MEAs beginswith their separation from the other compo-nents, after which they are shredded. Thisshredded product can then be processed eitherby hydrometallurgical means (metal leachingand filtration) or via a pyrometallurgicalprocess (incineration/melting followed by dis-solution). Both options yield precious-metal-

containing solutions that can be chemicallyrefined to isolate highly purified forms of thedesired metals.

Recycling precious metals from MEAs ischeaper than mining new raw materials. It isalso compatible with high yield requirements,particularly when the metals are in high con-centrations to start with. The flip side is thatbecause of the materials used, the recycling ofMEAs comes with significant process-engi-neering challenges. Most of today’s MEAs arebased on fluorinated hydrocarbons: the typi-cal elemental composition of an MEA for a sta-tionary application might be 32.3% fluorine,compared with 2.1% platinum and 0.4% ruthe-nium. The high concentration of fluorinemeans that considerable amounts of toxichydrogen fluoride and other fluorinated gasesare emitted when the MEAs are incinerated orsmelted in conventional processes.

With this in mind, hydrometallurgicalrecycling, which does not involve incineration,might seem like the better approach. The trou-ble is, yields from hydrometallurgical recyclingof platinum and ruthenium are lower (thanfrom the pyrometallurgical route) and thetreatment of the fluorine- and precious-metal-containing residues that are left over post-pro-cessing is far from straightforward. For thesereasons, Umicore sees the pyrometallurgicalroute as preferable and has developed a tech-

nique that pre-treats MEAs to avoid the gener-ation of toxic gases in the first place.

Umicore’s approach, which is currently inthe process of being patented, is to add an inor-ganic compound to the shredded MEA prior toincineration. This compound binds and neu-tralizes the fluoride ions so that they aretrapped and cannot react to form toxic gases.Other key process steps of the recyclingscheme remain unchanged. This simplifiesthings because it reduces the need for filtersand other components to clean the wastegases. It also reduces the recycling cost andeliminates scale-up problems associated withhandling fluorine-containing gases.

It’s all in the timingThe new technique, which was developed byUmicore’s fuel-cell and precious-metal refin-ing divisions, registers precious-metal yields ofat least 90% (and this figure can be higherdepending on the composition and metal con-centration of the scrap material). Ultimately,Umicore predicts that platinum recovery fromfuel cells could be greater than 95%, althoughsome metal loss is unavoidable during thecomplex initial separation and refining steps.

Technical progress notwithstanding, thetiming for commercial implementation andscale-up of the new process depends on theprogress of the fuel-cell industry as a whole.

A strategic approach to precious-metals management can help fuel-cell companies cope with unexpected price volatility.

Recycling pays its wayPrecious metals

Heavy metal: Umicore says that its metals smelter and refinery in Hoboken, Belgium, can beadapted to incorporate the latest techniques for precious-metals recycling from MEAs.

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

Soon to be the world’s largest fuel-cell-pow-ered vehicle, a 109 tonne railway locomotive isbeing developed by an international consor-tium. The locomotive will be powered by anarray of eight proton-exchange-membrane(PEM) fuel-cell modules, which develop a totaloutput of 1.2 MW.

The project was described in a paper pre-sented by Arnold Miller and colleagues at TheFuel Cell Seminar in San Antonio, Texas, inNovember. Miller is president of VehicleProjects LLC of Denver, Colorado, which isleading the five-year programme that began inMay 2003. The company has already built afuel-cell-powered locomotive for use in minesand is currently working on a fuel-cell/battery-powered mine loader. According to Miller, les-sons learned from this latest project will beapplied to the development of even larger fuel-cell-powered vehicles, including naval ships.

Each fuel-cell module is self-contained andprovides 150 kW of power. The modules arebeing created by AeroVironment of Monrovia,California, which will also integrate modulesand assemble the power plant. Nuvera Fuel Cellsof Milan, Italy, is supplying its FORZA fuel-cellstacks. According to Miller, the FORZA stackswere selected because they employ rugged andcompact metal bipolar plates.

The modules are connected in parallel toprovide an output voltage of 600 V and currentof 2000 A. The net output of the array is about1.0 MW, because components such as waterpumps and air compressors use approxi-mately 13% of the power generated. Water isextracted from the fuel-cell exhaust using aradiator and cyclonic water separator. Thiswater is then used for both stack cooling andmembrane humidification via a direct-water-injection system. Cathodic air is provided tothe fuel-cell stack at 1.5 bar absolute pressureusing an electric air pump.

Hydrogen will be stored on-board in areversible metal-hydride system, which waschosen because it offers a compact, low-pres-sure and efficient storage mechanism. The loco-motive is expected to operate for 30–40 h as aswitcher from 250 kg of on-board hydrogen.Refuelling is expected to take about 30 min.Metal-hydride systems tend to be heavy, butMiller said that this is not a problem for railwayapplications. The on-board storage system isbeing created by HERA Hydrogen StorageSystems of Longueuil, Canada.

In the long term, there are plans to developa system for the off-board production ofhydrogen using anhydrous ammonia, andexplore the on-board production of hydrogenusing this technique. According to Miller,ammonia is an attractive fuel for rail trans-port because it has a high energy density andis a renewable source of energy that is not car-bon-based. In addition, it can be transportedeasily by rail and is nonflammable. On thedownside, exposure to the chemical can causesevere tissue irritation. “The feasibility/con-ceptual design phase of the project concludedthat ammonia is a reasonable fuel, but wedecided to leave it to a later project for imple-mentation,” added Miller.

The locomotive will be designed for commer-cial and military use and the project is adminis-tered and funded by the National AutomotiveCenter (NAC) of the US Army Research,Development and Engineering Command. AUS Army diesel–electric locomotive is beingrefitted with the fuel-cell system. Four DC elec-tric motors will provide traction. The locomo-tive will be tested performing non-tacticalmilitary-railway tasks and it will also supplyelectricity to a military base.

The ultimate goal of the project is to developfuel-cell locomotives for use in commercial railtransportation. The range of possible applica-tions includes utility locomotives for switch-ing, subway trains, light rail, high-speed trainsand freight transport. Hamish Johnston

TECHNOLOGY TRACKING

Work on fuel-cell-powered locomotives looks to be on the right track.

Slow train comingSpecialist transportation“Umicore expects fuel cells to play an impor-

tant role in future energy supply and use, butpredicting when significant volumes willappear is difficult,” noted Roland Burmeister,the group’s vice-president for marketing, salesand applied technology for fuel cells. “Theadvantage is that you can watch what is goingon with today’s new fuel-cell products to pre-dict the associated demand for recycling.”

Yet Umicore has gone further than simplydeveloping a new process and waiting to seewhen it will be required. In the late 1990s, thecompany built an integrated metals smelterand refinery in Hoboken, Belgium. Each year,the new plant takes 250 000 tonnes of indus-trial and consumer recyclable products andby-products from other smelters and refiners.From this mixture, the plant derives preciousmetals, base metals, special metals, chemicalsand aggregates for concrete.

Significantly, executives claim that theHoboken plant can be easily adapted toimplement the new precious-metals recyclingtechnology for MEAs. “We can handle themarket needs today, but can build up the newprocess in parallel with current systems tomeet future demands,” explained ChristianHagelüken, head of business developmentand marketing at Umicore’s precious-metalsrefining division.

Preparation is everythingAt the same time, Umicore acknowledges thatdeveloping state-of-the-art recycling facilitiesis only half the battle. The fuel-cell industrymust also embrace the benefits of recyclingand address the challenge of collecting thescrap materials. This is particularly an issuewith portable devices that are frequentlyreplaced, and with automotive applicationswhere ownership may change several times.“Timing and volumes will determine whichapplications will recognize the need for recy-cling first,” explained Katharina Seitz,Umicore’s vice-president for R&D in fuelcells. “Ideally, we should be recycling the pre-cious metal from all product applications.”

Governments can also play a role in gettingthe message across. While no regulations cur-rently exist for fuel-cell recycling, the EuropeanUnion has already introduced requirementsfor recycling electronics scrap, and similar leg-islation exists for recovering the precious met-als from the catalytic converters in vehicles. Inthe US, a recommended practice for fuel-cellrecycling has been published by the Society ofAutomotive Engineers. And existing collectionand reclamation processes are expected to beeasily extended to fuel cells when they begin tobe used in significant volumes in cars.Siân Harris

Big train: the US Army is funding developmentof the fuel-cell locomotive. Testing will involvenontactical military-railway tasks.

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

TECHNOLOGY TRACKING

The direct-methanol fuel cell (DMFC), a systemin which methanol fuel is electro-oxidizeddirectly, without any preprocessing, to gener-ate electrical power, is starting to figure promi-nently on the near-term technology roadmapsof consumer-electronics manufacturers. Thesemicro fuel cells are set to enhance the perform-ance and ease-of-use of all sorts of electronicgadgetry – including laptop computers, mobilephones and video cameras – by providingextended run times per recharge (refuel) com-pared with conventional batteries. They mayalso hold the key to power delivery in “con-verged” communications devices that com-bine the latest colour-display technology withvoice, broadband data and video applications.

There’s just one problem in many DMFC sys-tems: membrane performance. Most recentDMFC activity has concentrated on proton-conducting poly(perfluoro-sulphonic acid)membranes, such as Nafion. These membranesexhibit a strong link between protonic conduc-tivity and methanol permeability – both prop-erties scaling with water content. Thepermeability to methanol is the source of so-called “methanol crossover”, a process whichsees the fuel migrate to the cathode side of thecell, where it typically reacts with oxygen. That’sa big headache for system designers because itreduces the run time for a given amount of fueland creates excess heat and water on the cathodeside of the cells. The result? A more complex,expensive cell architecture.

Now, however, a potentially disruptiveDMFC membrane is entering the commercialarena – one that could shake things up byaddressing methanol crossover and other per-formance issues head on. The new membranebeing pushed by US start-up PolyFuel is basedon hydrocarbon polymers rather than poly-fluorinated materials. And it’s because of thisalternative chemical composition, saysPolyFuel’s chief executive officer Jim Balcom,that the product exhibits a methanol crossoverbetween 50–65% lower than that of the mostcommonly used DMFC membrane,Nafion 117. That’s good news, because lowermethanol crossover means the DMFC systemcan use higher concentrations of methanol,which in turn means better fuel utilization.

Traditional DMFC systems operate withmethanol concentrations of between about 0.3and 1 M, with fuel crossover of the order of40%. Efforts to cut down on methanol

crossover via changes in membrane thicknessare usually accompanied by reductions in theprotonic conductivity. Furthermore, whilecrossover can be reduced by clever anodedesigns, these typically involve other systemcompromises. PolyFuel’s DMFC membrane,on the other hand, can cope with concentra-tions of up to around 8 M, and has a crossoverspecification of approximately 15%.

Another advantage of the new membrane,says Balcom, is that it exhibits only half of thewater flux or electro-osmotic drag (EOD) ofequivalently performing perfluorinated mem-branes. EOD involves the transfer of waterfrom the anode across the membrane to thecathode – the molecules being “pulled” acrossby the proton-transfer process. Like methanolcrossover, EOD places severe demands on sys-tem designers, because effective removal ofcathode water requires significant air-flow atnon-zero pressure – such that the air pump

(compressor) can be the largest source of para-sitic energy loss in the DMFC system. Tacklingthe EOD problem enables DMFC systems to be“smaller, lighter, less expensive and moredurable”, claims Balcom. Indeed, he reckonsthat a portable fuel cell built around the com-pany’s membrane can run for 30 to 35% longerthan a system built with an equivalently per-forming perfluorinated membrane.

PolyFuel is based in Mountain View,California, and was spun out of SRIInternational (formerly the Stanford ResearchInstitute) in 1999 with a remit to capitalize on14 years of know-how and intellectual prop-erty in the field of fuel-cell membranes. So far,PolyFuel has attracted some $40 m in funding,including an $18.4 m round back in July. It hasalso received a $3 m grant from the USDepartment of Energy to work on a portablefuel-cell application alongside Intel. Siân Harris

Will clever materials science and system-level understanding give PolyFuel’s engineered membranes the competitive edge? Maybe.

Disruptive technologyInnovation

If DMFCs represent the here and now forPolyFuel, then it’s encouraging to see that thecompany also has one eye on what happensfurther down the road. More specifically, itsdevelopment engineers in Silicon Valley arebusy working on a new class of membranes –also based on hydrocarbon polymers – forapplications in automotive fuel cells.

PolyFuel believes that its approach canmitigate many of the shortcomings associatedwith traditional proton-exchange-membrane(PEM) automotive fuel cells – i.e. high cost,narrow temperature range, poor durability andlimited lifetime. Its approach involvesengineering a self-assembling polymer thatincludes structural components (to givestrength and stability) and conductingcomponents (for enhanced protonicconductivity). The way that these polymers self-assemble means that the conductive blocksare held together tightly, “and because they aremuch closer than conducting blocks in othermembranes they can operate at a much lowerhumidity,” added Balcom.

According to in-house tests, the newmembrane reduces the relative humidity that isrequired from 80% (typical) at 80 °C to 50% at80 °C. In fact, stable operation is possible at 35%

relative humidity and at temperatures of up to95 °C. In addition, when compared with typicalperfluorinated membranes, PolyFuel claimsthat its membrane “is more than twice asstrong, more than 16 times as stiff and has fourtimes less hydrogen permeability”, all of whichhelps to enhance durability andmanufacturability. Even so, there are problemsto be overcome. “Applying catalysts tohydrocarbons is very different and much morechallenging than with fluorinated membranes,”conceded Balcom.

The long-term play

It’s a wrap: PolyFuel is developing advancedmembranes for portable DMFCs and for PEMautomotive fuel cells.

T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5

TALKING POINTWhere the fuel-cell industry has its say on emerging technologies.

New partnerships, new opportunitiesPolicy-makers and executives must combine creativeleadership with focused investment and innovativerevenue-generation models if they are to fast-trackthe emergence of fuel-cell technologies and markets.Robert Rose, executive director of the US Fuel CellCouncil, suggests how industry can make it happen.

“We mustmobilize tohelp ourgovernmentsto help us.”

Two years ago, more than 40 organizations endorsed “FuelCells and Hydrogen: the Path Forward”, a comprehensive$5.5 bn programme for the US. There were two reactions:you’ll never get the money; and it’s not enough. The criticswere half right. The US has come pretty close to therecommended budget so far. But it’s not enough. If we aregoing break our addiction to nonsustainable energy, wewill need 10 times that amount – about $60 bn – in the US,and three to four times as much as that worldwide, over thenext 15 years. What’s more, we’re going to need adedicated revenue stream to pay for it.

Our economies are shaped by the geopolitics of oil andthe consequences of carbon-based fuels. What this meansto our world can be read about each day in any newspaper.What it means to our industry can be summed up in asingle word – opportunity. If we can get products tomarket, we can make money, and in the process do theworld a world of good.

Getting to market will require us to form newpartnerships, both inside our industry – so that webecome an effective force for change – and outside it, withgovernments who see fuel cells and hydrogen as tools tobuild better lives for people. In markets in which goodtechnology is already entrenched, market forces will needsome turbocharging from governments. This is not asradical as it may sound – governments influence marketsall the time. Government programmes are not shaped in avacuum and policy-makers do best when they areresponding to clear messages from the governed. So wemust mobilize to help our governments to help us.

We must be the leadersFuel cells will be up to the task. We are making impressivetechnical progress: better stack and system lifetimes,growing confidence on cost reduction, and terrificperformance for fuel-cell vehicles in demonstrationprogrammes. And let’s not forget that fuel-cell generatorsare out in the field, meeting customer needs, today. Here’swhere our governments can help, though. At their best,governments bring credibility that is valuable inboardrooms and in the media. They are good at sharing thecost of high-risk research and stimulating collaboration.They can support market introduction by subsidizingearly purchases. They can use their purchasing power,matching our products’ capabilities with real-world needs.

A 15-year, $60 bn public–private partnership in the USequates to $4 bn a year – less than the US pays for importedoil in two weeks. With comparable efforts internationally,this sort of investment is consistent with commercial

expectations. The International Energy Agency (IEA)added up estimates of the global cost of a transition to ahydrogen economy over the next 30 years and came upwith $1–5 tn. Admittedly, this is a huge sum of money. Yetit is only about 0.3% of global national product, andmodest compared with the cost of similar transitions fromcanal to rail and rail to motor car, which the IEA estimatescost between 5 and 10% of global product.

So what would a $60 bn programme look like? Here aresome suggestions. If they touch off a raging argument, somuch the better. First, we need targets that will help makethe programme understandable to the average citizen.The Japanese have set targets of 10 GW of fuel-cell powerand 5 million vehicles by 2020. A US programme only halfas ambitious (as a percentage of market penetration)would include 8 million fuel-cell vehicles (3% of thevehicle fleet) and 20 GW of fuel-cell power generation (2%of installed capacity). Let’s also aim at 20% of what I callpersonal-power markets. If all this sounds like a stretch,remember it isn’t 2020 yet. These are goals, notpredictions. But they will help us focus our efforts.

Second, we should spend about $30 bn on research,demonstration and infrastructure, and $30 bn onmarket stimulation through government purchases,purchase subsidies and tax incentives. Here’s a “strawman” proposal for the US: $10 bn for coordinatedresearch and demonstration programmes; $10 bn foruniversity-led research; $10 bn to help finance a nationalhydrogen infrastructure; $10 bn for governmentpurchases and purchase subsidies for fuel-cellgenerators; $16 bn for fuel-cell-vehicle purchases andtax credits; and $4 bn for purchase of portable power-units that meet users’ expectations.

To make sure the commitment endures, a dedicatedrevenue stream is essential. Just to make sure I offendevery possible interest, I’ve put a list together. Each ofthese proposals would raise about $4 bn a year in the USand between $12 bn and $20 bn if applied worldwide: ● A 3 cent increase in the gasoline tax; US prices can fluctu-ate more than that in one week.● A tiny per-kilowatt-hour fee on utility generation – one-sixth of one cent. ● A 60 cent per barrel fee on oil .● A $4 dollar per tonne fee on coal sales.● A 60 cent per tonne fee on greenhouse-gas emissions.● A $17 annual federal vehicle registration fee. Such a fee onvehicles worldwide would produce nearly $13 bn a year.

If we do succeed in this endeavour, we will achievenothing less than an overhaul of the engine of the world’seconomy, making each nation safer and offering thosenations that have been left out of the oil century a chancefor a better future. A 15-year programme is just thebeginning. But begin we must, and now. It is our job –yours and mine. There is no better calling.

● This is an edited version of a speech given at The Fuel CellSeminar in San Antonio, Texas, in November 2004.

Robert Rose,executive director ofthe USFCC and theBreakthroughTechnologies Institute.

Burnout: can the worldkick its addiction tohydrocarbon fuels?

C O P Y R I G H T I N S T I T U T E O F P H Y S I C S A N D I O P P U B L I S H I N G L T D 2 0 0 5 T H E F U E L C E L L R E V I E W | D E C E M B E R 2 0 0 4 / J A N U A R Y 2 0 0 5 | F C R . I O P . O R G

THE

FUEL CELL REVIEWCompetitive intelligence on hydrogen and fuel-cell technologies

Subscription order form

✓ Are you working in the fuel-cell supply chain?

✓ Would you like to learn direct from the industry experts?

✓ Do you want to be kept up-to-date on R&D and technology transfer?

✓ Do you find it hard to source authoritative analysis of the latest technological advances?

✓ Would it save you time and effort to find all your information needs in one publication?

✓ Would you like to SAVE up to 35% on the cost of a subscription?

SUBSCRIBE TODAY AND SAVE UP TO 35%

✓ Yes, I would like to subscribe to The Fuel Cell Review

■■ 1 year (6 issues) £149/$269/¤219

■■ 2 years (12 issues) £224/$404/¤329 - SAVE 25%*

■■ 3 years (18 issues) £291/$525/¤427 - SAVE 35%*

Rates for libraries available on request*offer ends 31 March 2005

Your details

Name:

Job title:

Company:

Department:

E-mail:

Address:

Postcode:

Country:

Tel: Fax:

Nature of business:

Three easy ways to pay

■■ Credit card - please charge my Amex/Visa/MastercardCard no. ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■Expiry date: ■■ ■■ / ■■ ■■

Signed:

Dated:

■■ Cheque made payable to IOP Publishing Ltd

■■ Please invoice me

■■ IOP Publishing Ltd may write to you about other services and products that may be of interest. Tick this box if you do not want to receive such information.

■■ Tick this box if you do not want to receive such information by e-mail.■■ IOP Publishing Ltd may occasionally pass your details on to other reputable companies

whose products and services may be of interest. Tick this box if you do not want to receivesuch offers.

CODE: AD2

Please return to

The Fuel Cell Review, Institute of Physics Publishing, Dirac House, Temple Back, Bristol BS1 6BE

Tel. +44 (0)117 930 1034 Fax +44 (0)117 930 1178 E-mail fcr@iop.org Web fcr.iop.org

No-risk money back guaranteeIf you are not entirely satisfied with this product, you can cancel yoursubscription at any time and receive a full refund for any unmailed issues – no questions asked!

If you answered YES to any of the above questions then you need look no further. The Fuel Cell Review is a uniquebimonthly publication that guarantees to deliver in-depth analysis and incisive commentary on the R&D, emergingtechnologies and applications that will take fuel cells into the main stream.

It will provide you with an informed perspective on the latest developments across all levels of the fuel-cell supply chain.Along with in-depth journalism from our in-house science and technology editors, every issue brings you the mostrespected names in the industry, reviewing the critical subjects of the day.

Valuable coverage you will not be able to find anywhere else.

Can you afford to miss an issue?Sample articles from each

issue are available for free onour website – fcr.iop.org

✃

http://www.solartronanalytical.com/fcr