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Highly Dispersed Alloy Cathode Catalyst for Durability

Sathya Motupally

June 10, 2008

This presentation does not contain any proprietary, confidential, or otherwise restricted information

Project ID # FC5

2This presentation does not contain any proprietary, confidential, or otherwise restricted information

HIGHLY DISPERSED ALLOY CATALYST

• Start – May 1, 2007• End – April 30, 2010• 33% Complete

A. Performance• Increase catalyst activity

B. Cost • Reduce Pt metal loading

C. Durability• Increase cyclic durability

• Total project funding– DOE share - $6.278M– Cost share - $2.860M

• DOE Funding received in FY07– $200K

• DOE Funding for FY08– $1,600K

Timeline

Budget

Barriers

• Johnson Matthey Fuel Cells

• Texas A&M University

• Brookhaven National Laboratory

Partners

3This presentation does not contain any proprietary, confidential, or otherwise restricted information

HIGHLY DISPERSED ALLOY CATALYSTTechnical Contributors

UTC Power:T.T. Aindow, Elise Izzo, Panadda Madden, Sathya Motupally, Tom Jarvi

Johnson Matthey Fuel Cells:Sarah Ball, Sarah Hudson, Rachel O’Malley, Brian Theobald, Dave

Thompsett, Graham Hards

Brookhaven National Lab:Wei-Ping Zhou, Jia Wang, Radoslav Adzic

Texas A&M University:Perla B. Balbuena, Gustavo Ramirez-Caballero, Yuguang Ma, Rafael

Callejas-Tovar, Julibeth Martinez de la Hoz

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Characteristics DOE 2010 Target DOE 2015 Target

Pt group metal (total content) [g/kW] 0.3 0.2

Pt group metal (total loading) [mg/cm2] 0.3 0.2

Mass activity @ 900mV [A/mg] 0.44 0.44

Specific activity @ 900mV [μA/cm2] 720 720

Cyclic durability @ <80°C / >80°C [h] 5000/2000 5000/5000

ECA Loss [%] <40 <40

Cost [$/kW] 5 3

DOE 2010 and 2015 Technical Targets

HIGHLY DISPERSED ALLOY CATALYSTObjectiveDevelop structurally and compositionally advanced cathode catalyst that will meet DOE 2010 targets for performance and durability

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Month/Year Milestone or Go/No-Go Decision

August 2008 Milestone: Bench scale dispersed alloy catalyst formulation

September 2008 Go/No-Go decision: Verification of down-selected dispersed alloy catalyst

October 2008 Milestone: Bench scale core/shell catalyst formulation

November 2008 Go/No-Go decision: Verification of down-selected core/shell catalyst

HIGHLY DISPERSED ALLOY CATALYSTMilestones

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Core/Shell Catalyst• Pd/Pt• Ir/Pt• Co/Pd/Pt• IrCo/Pt• PdxCoy/Pt• Pt/Au

Modeling• Core/shell structuralstability• Core/shell durability• Impact of shell

thickness• Impact of sub-layer

composition

Alloy Catalyst• Ir-containing ternary• Alternative support• Alloy fundamentals• Synthesis optimization

HIGHLY DISPERSED ALLOY CATALYSTApproach

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0.88 A/mgPt

Mass activity

Cyc

lic D

urab

ility

0.0 A/mgPt

0 h

2010 Target

PtIrCo

Q1, ‘08

Q1, ‘08PtIrM

Q3, ‘08

Q3, ‘08

Structural and composition optimization

Core element, shell thickness optimization

Future core

Shell synthesis

Option 2

PtIrM core/shellOption 1

0.44 A/mgPt

5000 h

HIGHLY DISPERSED ALLOY CATALYSTStrategy

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Surface Segregation Model for Pt3M Alloys

Y. Ma and P. Balbuena, Surface Sci. 602, 107-113, (2008)

HIGHLY DISPERSED ALLOY CATALYSTModeling – Segregation energies for Pt3M alloys

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Eseg(eV) Pt3Ir(111) Pt3Co(111) Pt3Fe(111) Pt3Ni(111)Under 0.25 ML of O

-0.04 0.14 0.45 0.20

-0.54Without adsorption

-0.61 -0.41 -0.38

Eseg: surface segregation energyPositive Eseg: core/shell structure energetically unfavorable

• Segregation behavior changes in the presence of oxygen• Most transition metals change from Pt surface segregation in the absence of oxygen to anti-segregation with oxygen

CORE/SHELL STABILITYEffects of Oxygen on Pt segregation

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In vacuum –Pd and Pd3Co cores increase Pt stability (positive potential shift) whereas Co, and Pd3Fe cores decrease stability

CV1

CV2

IMPACT OF CORE/SHELL ON Pt DISSOLUTIONPotential shift with monolayer Pt shell in vacuum

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In the presence of oxygen –Pt becomes less stable compared with in vacuumPd and Pd3Co cores can increase Pt stability

0.25 monolayer of oxygen

IMPACT OF CORE/SHELL ON PT DISSOLUTIONPotential shift with monolayer Pt shell with oxygen

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• Oxide observed in the as-received state• Reduction using hydrogen leads to further increase in mass activity

20 40 60

Ir(111)

2θ (degree)

IrO2(111)

Ir(200)

* * * *

as received_UTC

H2; 500 C

0.0 0.2 0.4 0.6 0.8 1.0-8

-6

-4

-2

0

2 50.6% TEC10E50E-HT Pt/C, 26.6 μgPt/cm-2

PtML on Ir/C

as received Ir/C, 3.6 μgPt/cm-2

reduced Ir/C at 500C by H2, 2.8 μgPt/cm-2

j /m

A c

m-2

E/V vs. RHE0.0

0.5

1.0

0.9 V

j k /mA

μg-1 Pt

50.6% TEC10E50E-HT Pt/CPtML on

Ir/C_as received Ir/C_reduced at 500 C by H2

CORE/SHELL IMPACT ON ACTIVITYIr/Pt Core/Shell – As received and H2 annealed

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• Pd3Co core gives the highest activity among all the Pd-Co alloys – 7x

• Chemistry for 20g scale-up underway• Mass activity normalized by 5 y average spot price ratio of PGM metals equals 0.70 mA/μgPGM and 0.38 mA/μgPGM for RDE and 300mg methods, respectively.

Pd3Co particle size: 5.5 nm0.0 0.2 0.4 0.6 0.8 1.0

-6

-4

-2

0 50.6% TEC10E50E-HT Pt/C, 26.6 μgPt/cm-2

PtML on Pd3Co/C_JM

R.D.E, 7.2 μgPd/cm-2,4 μgPt/cm-2

300 mg batch, 7 μgPd/cm-2,6.5 μgPt/cm-2

j /m

A c

m-2

E/V vs. RHE

0.1 M HClO4

10 mV/s; 25 0C1600 rpm

0

1

2

0.9 V

j k /mA

μg

-1 Pt

50.6% TEC10E50E-HT Pt/CPtML on Pd3Co/C_JM

R.D.E. 300 mg batch

0.00

0.25

0.50 50.6% TEC10E50E-HT Pt/C

PtML on Pd3Co/C-JM R.D.E 300 mg batch

0.9 Vj k /m

A μg

-1 Pd+P

t

CORE/SHELL IMPACT ON ACTIVITYPd3Co/Pt Core/Shell

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0.0 0.2 0.4 0.6 0.8 1.0 1.2-200

-100

0

100

PtML on Pd3Co/C_JM, 300 mg batch initial after 3k cycles

i /μA

E/V vs. RHE

0.1 M HClO4

20 mV/s

0.0 0.2 0.4 0.6 0.8 1.0-8

-6

-4

-2

0

0 10 20 30

0.75

0.90

1.05

E/V

vs. R

HE

time (s)

PtML

on Pd3Co/C

initial after 3k cycles

j /μA

cm

-2E/V vs. RHE

0.1 M HClO4

10 mV/s, 1600 rpm

• Pd3Co/Pt core/shell cyclic resistance -no apparent activity loss after 3000 cycles

0.7_1.05V, 10 sec, RT

CORE/SHELL IMPACT ON ACTIVITYPd3Co/Pt Core/Shell

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40% Pt2IrFeICP: 38.3% wt. Pt, 17.1%Ir, 7.0%FeECA: ~46 m2/g PtMass Activity: ~0.24 A/mg PtSpecific Activity: ~649 μA/cm2

40% Pt2IrCrICP: 39.2%Pt, 17.8%Ir, 4.4%CrECA: ~63 m2/g PtMass Activity: ~0.17 A/mg PtSpecific Activity: ~281 μA/cm2

40% Pt2IrCo = BaselineICP: %Pt; %Ir; %CoECA: ~44m2/gPtMass Activity: ~0.20 A/mgPtSpecific Activity: ~544 μA/cm2

0

10

20

30

40

50

60

70

80

90

100

Pt2IrFe Pt2IrCo Pt2IrCr

ECA (m2/gPt)MA (mA/10mgPt)SA (uA/10cm2)

HIGHLY DISPERSED ALLOY CATALYSTAlternative Ir containing alloys

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• Modeling– Impact of oxygen on Pt dissolution and structural stability for various

core/shell systems has been quantified• Core/Shell(Pt) Catalyst

– A number of elemental and alloy cores have been evaluated; Pd3Co and Ir cores lead to the highest improvement in ORR

• Alloy Catalyst– Various PtIrX alloys have been synthesized and tested to understand

activity and durability trade-off• Future Work (2008)

– Pd3Co/Pt, Ir/Pt core/shell durability and scale-up optimization– IrxCoy alloy cores – Validate modeling results on core/shell stability and durability

• Future Work (2009)– Down-select optimum catalyst from dispersed or core-shell catalyst– Validate full scale single-cell fuel cell

SUMMARY AND FUTURE WORK