“solar energy to fuels if a leaf can do it we can do it. · “solar energy to fuels. if a leaf...

“Solar energy to fuelsIf a leaf can do it we can do it".

Lee Kuan Yew NTU Lecture10th November 2008

James BarberImperial College London

Mean Global Energy Consumption Rate

4.52

2.7 2.96

0.286

1.21

0.2860.828

0

1

2

3

4

5

TW

Oil Coal Biomass NuclearGas Hydro Renew

Total: 14TW U.S.: 3.3TW

Over 85% from fossil fuel

Map of the world based on population

From M. Newman

Map of the world based on energy consumption

From M. Newman

“2H2” + CO2 (CH2O)Fuel

(Organic molecules)

But why not do what the leaf does?

But needs H2 -Where does it come from?

2H2O O2+ “2H2”

Solar Energy

From Water

2H2O O2+ “2H2”

Solar Energy

“2H2” + CO2 (CH2O)Organic

molecules

Two basic reactions of photosynthesis

Macroscopic Reaction Vessel

2H2O O2 + 4H+ + 4eSunlight

Organic moleculeof life

+CO2

1000 millions years to producefossil fuels and used in ~ 1000 years

0rOne year of fossil fuel consumption =one million years of photosynthesis

5 Billion Year Clock

Global Photosynthesis “The Engine of Life”

2H2O 4H+ + 4e CH2OOrganicmolecules

CO2

CO2

O2

O2

Solar Energy(100,000 TW)

photosynthesis

respiration biomassfood

fossil fuelscombustion

light reactions dark reactions

Biology adopted the perfect solution to the energy problem

EnergyDecreased entropy

& heat 200 TW

0.2% efficiency

“Cyclic”

2H2O O2+ “2H2”

Solar EnergyLight reactions

“2H2” + CO2 (CH2O)Organic

molecules

Dark reactions

Two basic reactions of photosynthesis

Thylakoid membranes(Light reactions)

Stroma(Dark reactions)

Photosynthetic efficiency

Lucky to get 2% dry matter and 0.5% starch/sugarwith inputs

Brazil (sugar)Bioenergy 30% of

total energy

~50% of cars sold in 2005were “Flex-Fuel” vehicles

able to use ethanol andpetrol

USA (corn) 6 million carsable to use E85

But only~2% of fuel

Miscanthus

5 tons of bioethanol/acre to be competitive at present(i.e. 5:1 conversion)

~ 30% of the US energy requirements

2005 USDA/DOE Report

Currently ~ 3%

But need solar energy conversion at 10% or better

The big loss factor

2H2O 4H+ + 4e Organicmolecules

CO2

CO2

O2

O2

Solar Energy

photosynthesis

respirationbiomass

food fossil fuelscombustion

light reactions dark reactions

Hydrogen

Hydrogenase

For high efficiency of energy conversion use the front end of photosynthesis“Light Reactions”

Solar Land Area Requirementsat 10% efficiency

6 Boxes at 3.3 TW Each

Ni-Fe typehydrogenase

Fe-S typehydrogenase

Hydrogenase

H2O Organic substrates

Hydrogen

(CH20)n

e/H+O2

green algaChlamydomonas

2H2O 2H2

O2

O2

Solar Energy (100,000TW)

EnergyTotal global (14TW)

Liquid fuel

One hour of solar =annual global energy consumption

H2/O2/H2O cycle driven by solar energy

The Perfect Solution“Cyclic”

+CO2

The Artificial Leaf

2H2O O2+ “2H2”

Solar EnergyLight reactions

The Water Splitting Reaction

5 Billion Year Clock

Big Bang ofEvolution

H2O splitting

Oxygenic atmosphere&

Ozone layer

Photosystem II (PSII) is the enzymefound in plants, algae and cyanobacteria

which uses solar energy to split water into molecular

oxygen and reducing equivalents

0

-1

+1

P680+

P680*Pheo-

PQA

PQB

RedoxscaleeV

P680+ is highly oxidisingEm ~ 1.3eV at pH 7

Tyrz (YZ)

H2O

Red.

Oxid.

Electron transfer in Photosystem II

H+

Water splitting reactionis a four photon process

2H2O + 2PQ O2 + 2PQH2Light (4hv)

PSII

+

+

+

2

S-state cycle – Kok & Joliot

dark stable state

Oxygen emission induced by flashesJoliot & Kok ~1969

Photosystem II (PSII)

Water splitting rapid turnover of D1“a repair process”

From Black Boxto

Atomic Resolution

SPEM

EC X-ray

PSII

1994

1995

1998

2001

2004

Plant PSII

Cyanobacterial PSII

Mn4CaO4

Photosystem Two: The water splitting enzyme

2H2O O2 + 4e + 4H+4hv

Ferreira et al Science 2004

Active Branch Protective Branch

Lumenal view of PSII monomer within the dimer

Oxygen Evolving CentreAnomalous diffraction for Mn (1.89A) and Ca

(2.25A)

bicarbonate?

Ferreira et al Science 303(2004)1831-1838

Water Splitting-Oxygen Evolving Catalytic Site

A344

Cubane-like Mn3CaO4 cluster linked to a 4th Mn by a mono-μ-oxo bond

6 + 1 Amino acid ligands5 + 1 D1 protein1 CP43

Diagrammatic representationof the water splitting

centre

CaO

O O

MnIV MnIV

O

MnIVMnV

O

OHighly electrophilic oxo (or oxyl radical)

S4

Nucleophilic attackH H Cl

a) hv

b) e-

c) e-

C60-Por-Bi-PhOH

Biomimetic Systems

Tom Moore andcolleagues

ASU

From Natural

A Q Q B

P 680

O

Mn

Mn

Tyr

Acceptor

N

EtO 2 C

NH

O

NN ON N

N NO OO

Me Me

Me

MnMn

Ru

NN

N

NN

to

Photosynthesis

Artificial

Hammerstrom & StyringU. of Uppsala

Fe

O

BOH

Design of an artificial water splitting system

H

MnIVMnIVMnIVMnV

O

OCa

O

OO

Cl

O

Daniel NoceraMIT

2H2O 2H2

O2

O2

Solar Energy

EnergyTotal global

Carbon basedfuels

The Artificial Leaf

+CO2

RuBisCO +H2O

Calvin Cycle

Crystal structure of RuBisCo isolated from spinach

Leonardo’s Dream

2H2O 2H2

O2

O2

Solar Energy (100,000TW)

EnergyTotal global (14TW)

“If a leaf can do it we can do it”

“Its only chemistry”

One hour of solar =annual global energy consumption

EnergyTotal global

(14TW)

Solar Energy (100,000TW)O2

O2

2H2O 2H2

The ArtificialLeaf

+CO2Liquid fuel

Our Dream

Jules Verne’s Dream (1875)

“I believe that water will one day be used as a fuel, because the hydrogen and oxygen which constitute it, used separately or together, will furnish an inexhaustible source of heat and light. I therefore believe that, when coal deposites are oxidised, we will heat ourselves by means of water. Water is the fuel of the future”

“If the leaf can do it, wecan do it”

I say -