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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– $1,600K
Timeline
Budget
Barriers
• Johnson Matthey Fuel Cells
• Texas A&M University
• Brookhaven National Laboratory
Partners
3This presentation does not contain any proprietary, confidential, or otherwise restricted information
HIGHLY DISPERSED ALLOY CATALYSTTechnical Contributors
UTC Power:T.T. Aindow, Elise Izzo, Panadda Madden, Sathya Motupally, Tom Jarvi
Johnson Matthey Fuel Cells:Sarah Ball, Sarah Hudson, Rachel O’Malley, Brian Theobald, Dave
Thompsett, Graham Hards
Brookhaven National Lab:Wei-Ping Zhou, Jia Wang, Radoslav Adzic
Texas A&M University:Perla B. Balbuena, Gustavo Ramirez-Caballero, Yuguang Ma, Rafael
Callejas-Tovar, Julibeth Martinez de la Hoz
4This presentation does not contain any proprietary, confidential, or otherwise restricted information
Characteristics DOE 2010 Target DOE 2015 Target
Pt group metal (total content) [g/kW] 0.3 0.2
Pt group metal (total loading) [mg/cm2] 0.3 0.2
Mass activity @ 900mV [A/mg] 0.44 0.44
Specific activity @ 900mV [μA/cm2] 720 720
Cyclic durability @ <80°C / >80°C [h] 5000/2000 5000/5000
ECA Loss [%] <40 <40
Cost [$/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
9This presentation does not contain any proprietary, confidential, or otherwise restricted information
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