novel non-precious metals for pemfc: catalyst selection ... · usc pemfc catalyst project...

Center for Electrochemical EngineeringUniversity of South Carolina

2004 DOE Hydrogen, Fuel Cells InfrastructureTechnologies Program Review

Branko N. Popov

Department of Chemical Engineering

University of South Carolina,

Columbia, South Carolina 29208May 25, 2004

Novel Non-Precious Metals for PEMFC:Catalyst Selection Through Molecular Modeling

and Durability Studies

This presentation does not contain any proprietary or confidential information


Project Objectives

Synthesize novel non-precious metal electrocatalysts with similaractivity and stability as Pt for oxygen reduction reaction.

High activity toward oxygen reduction reaction.Mass production method.Corrosion resistance.Low cost.

Improve understanding of reaction mechanism of oxygen reductionon non-precious catalysts through

Theoretical molecular modeling.Electrochemical characterization.Structural studies (XPS, EXAFS, XANES).Correlation between the catalyst composition, heat treatment andcatalytic sites for oxygen reduction.

Demonstrate the potential of the novel non-preciouselectrocatalysts to substitute Pt catalysts currently used in MEA.


Project Budget

Total

$84,537

Indirect

$18,892

Direct

$65,645

Case Western

Reserve Univ.

Total

$50,468

Indirect

$18,425

Direct

$32,043

Northeastern

University

Total

$325,000

Indirect

$108,615

Direct

$216,385

Cumulative

Year 1

Total

$189,995

Indirect

$71,298

Direct

$118,697

University of

South Carolina


Technical Barriers and Targets

Electrode performancePerform at least as good as the conventional Pt catalysts

currently in use in MEAs

Durability2000 hours operation with less than 10% power

degradation

Material Costcost at least 50% less as compared to a target of 0.2 g

(Pt loading)/peak kW


Catalyst Development

Mathematical modeling

for alloy optimization

Metal/ Alloy

Nitrogen Treatment

Chalcogenide

Structure, property

analysis

MEA TestDurability Studies

Catalyst Synthesis,

RRDE test

Modified Carbon

substrates


Project Timeline

Task Summary

and DurationSubtask Duration

End date for task Task Milestone Project links


Project Safety

• All reactors are operated in a vented area

• Hydrogen detector is placed near the hydrogen source

• Reactors using high concentrations of hydrogen haveadditionally installed a burning flame to eliminateexhausting gas

• All the reactors have being design using leak-proofjoints

• Ambient atmosphere pressures are used at all times inthe reaction vessels and fuel cell stations

• Only personnel trained in how to operate the reactorsand emergency procedures is allowed to use thereactor set-up

– At least one person trained must present duringruns in case of an emergency shutdown


Safety Equipment

Furnace for Hydrogen Treatment

at High Temperature

and Safety Equipment

PEM Fuel Cell Dual Station

with a Hydrogen Sensor


Experimental Set-Up for High Temperature HeatTreatment to Prepare Non-Precious Catalyst


Our Approach

Develop supported and unsupported catalysts for oxygen reduction- Nitrogen contained precursors- Transition metal precursors- Chalcogenide compounds

Optimize number of the catalytic sites as a function of– Carbon pretreatment.– Chemical composition of catalyst.– Post treatment of catalyst.

Accomplish low cost catalyst through– Mass production methods.– Non precious metals.– Low cost precursors.

Accomplish stable non precious catalysts with– High durability (corrosion resistant alloy catalysts).– Low peroxide generation.– High activity towards oxygen reduction.


AccomplishmentsDisk Current of Metal Free Catalyst for Oxygen Reduction

Reaction at 900 RPM

E/V vs NHE

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

i/A

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

K1 (Bare Ketjen - No pre-treatment)

K2

K3

K4

K5

K6K7


Current Trends in Non Noble Metal Catalyst forOxygen Reduction and Comparison of Cost

J. Electro.Anal. 541

(2003) 147$30.1/ 1g

CoTMPP(cobalt tetramethoxy phenyl porphyrin)

$0.2 /1gPrecursors used in our study

$80/ 1g

$12.6/ 1g

$43/ 1g

Electrochem.Acta 41 (1996)

1689

J. PowerSources, 46(1993) 61

CoTPP(Cobalt tetraphenyl porphyrin)

CoPC(Cobalt phthalocyanine)

H2PtCl6(Chloro platinic acid)


Develop Supported and UnsupportedCatalysts for Oxygen Reduction

Fe, Co and Cr were loaded on carbon.

Metals loaded on carbon was followedby several post treatments to obtainoxygen reduction catalysts.

The catalysts are tested for oxygenreduction activity by RDEmeasurements

Catalyst Loading

Post Treatments

RDE measurements


Potential (E vs NHE)

0.0 0.2 0.4 0.6 0.8

Ct (

A/

2)

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

ETEK 20% Pt/C 8 µg/cm2

CrX - 40/7 wt %

Cr - 10 wt%

Effect of Addition of X to Cr/C toward OxygenReduction Reaction at 900 RPM

Treatment III

E1/2 = 0.532

E1/2 = 0.572

E1/2 = 0.576


Disk Potential E/V vs SHE

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Di

k C

t i/A -1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

Co/C

Co-X/C

E-TEK 20% Pt-14 µg Pt/cm2

Effect of Addition of X to Co/C toward OxygenReduction Reaction at 900 RPM

E1/2

= 0.49

E1/2

= 0.61

E1/2

= 0.62


Effect of alloying for the Different TransitionMetal Based Catalysts

Disk current at scan rate of 5mV/s rotated at 900 rpm

E/V vs NHE

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

/

-1.0

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

47 % Fe-X

47 % Fe Alloy-X

14µg Pt/C

47 % Fe

E1/2 = 0.598 V vs. SHE

E1/2 = 0.4740 V vs. SHE

E1/2 = 0.623 V vs. SHE

E1/2 = 0.6202 V vs. SHE


Effect of Treatment on Oxygen reduction forUnsupported Chalcogenide Catalysts at 900 RPM

E/V vs. NHE

0.0 0.2 0.4 0.6 0.8 1.0 1.2

I/A

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

CoSe B, E1/2

=0.1502V

CoSe A, E1/2

=0.334V

MoFeSe B, E1/2

=0.2435V

MoFeSe A, E1/2

=0.3755V

MoRuSe B, E1/2

=0.57V

MoRuSe A, E1/2=0.66V

Pt, 20µg/cm2

B: Before treatment; A: After treatmentB: Before treatment; A: After treatment


Potential (E vs NHE)

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Ct (

A/

2)

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

200 rpm

400 rpm

600 rpm

900 rpm

1200 rpm

1500 rpm

Ct (

A2

)

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

200 rpm

400 rpm

600 rpm

900 rpm

1200 rpm

1500 rpm

Disc and Ring currents obtained for CrX/C alloy catalyst

Treatment III 900rpm

E1/2 =0.572 V


Average Number of Electrons Transferred and %Peroxide Produced in Co/C and Co-X/C

Disk Potential E V vs SHE

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

A 2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2 Co/C

Co-X/C


Disk Potential E V vs SHE

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

% H

2

O2

0

20

40

60

Co/C

Co-X/C



Comparison Between Non Precious Catalystand Commercial Pt/C Catalyst

193.60.62Fe alloy-X/C

57.52.850.49Co/C

313.30.47Fe/C

2.53.950.61CoX/C

7.843.90.572CrX/C

103.80.6724 µg Pt/cm2

(20wt% Pt/C)

3.9

3.6

Average No. ofElectrons

0.66

0.506

E half(V vs. NHE)

2.7

20.29

%H2O2

Cr/C

MoRuSe/C

Catalyst


Conclusions

• Novel non-precious metal catalysts were developed foroxygen reduction which have performance comparableto Pt under RRDE test conditions.

• Novel treatments were developed for synthesis of Cr-XCo-X, Fe-X and Mo-Ru-S. These alloys have improvedactivity for oxygen reduction , with number of exchangeelectrons close to four and showed a decreasedactivity for H2O2 generation.

• The pretreatment, the allying element and the posttreatment are critical in order to obtain high catalystperformance.


Dr. Branko Popov

PI and Team Leader,

University of South Carolina

(Development of Novel Catalyst)

Dr. Sanjeev Mukherjee

(XANES Studies on Catalysts)

North Eastern University

Dr. Ralph White

Dr. John Weidner

(Modeling of Catalyst Kinetics and

Catalyst Stability)

Dr. John Vanzee

University of South Carolina

Dr. Al Anderson

Case Western Reserve University

(Molecular Modeling of Catalyst)

Interactions & Collaborations


Future Work

• To decrease the alloy activation overvoltage byoptimizing the wt % of the catalyst and the alloyingelement.

• To increase the active sites for oxygen reduction byoptimizing the post treatments.

• To study nitrogen containing precursors for oxygenreduction.

• To define the structural properties of the of active site.• To optimize the catalyst performance through molecular

modeling.• To perform stability studies.• To perform MEA testing.

novel non-precious metals for pemfc: catalyst selection ... · usc pemfc catalyst project...

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