V–121FY 2013 Annual Progress Report DOE Hydrogen and Fuel Cells Program

Dr. Silvia Wessel (Primary Contact), David HarveyBallard Power Systems9000 Glenlyon ParkwayBurnaby, B.C. V5J 5J8Phone: (604) 453-3668Email: silvia.wessel@ballard.com

DOE ManagersKathi Epping MartinPhone: (202) 586-7425Email: Kathi.Epping@ee.doe.gov David PetersonPhone: (720) 356-1747Email: David.Peterson@go.doe.gov

Technical AdvisorJohn Kopasz Phone: (630) 252-7531Email: kopasz@anl.gov

Contract Number: DE-EE0000466

Subcontractors:• GeorgiaInstituteofTechnology,Atlanta,GA

(Dr. S.S. Yang)• LosAlamosNationalLaboratory,LosAlamos,NM

(Dr. R. Borup)• MichiganTechnologicalUniversity,Houghton,MI

(Dr. J. Allen)• Queen’sUniversity,Kingston,Ontario,Canada

(Drs. K. Karan, J. Pharoah)• UniversityofNewMexico,Albuquerque,NM

(Dr. P. Atanassov)

Project Start Date: January 1, 2010 Project End Date: March 31, 2013

Overall ObjectivesIdentify/verifycatalystdegradationmechanisms•

Correlatecatalystperformance/catalyststructuralchange•asafunctionofunitcelloperationalconditionsandcatalystlayermorphology/composition

Developkineticandmaterialmodelsforcatalystlayer•aging, i.e., macro-level unit cell degradation model, micro-scale catalyst layer degradation model, and moleculardynamicsdegradationmodeloftheplatinum/carbon/ionomerinterface

Developdurabilitywindowsandmitigationstrategiesfor•catalystdegradationthroughmodificationofoperational

conditionsandcomponentstructuralmorphologies/compositions

Fiscal Year (FY) 2013 Objectives SimulatePtdissolutionandtransportofPtspeciesinthe•ionomer using the developed Molecular Dynamics Model

Completethe2-phaseflowtransientmicro-structural•catalystmodelandsimulationofeffectiveproperties

Recodetheone-dimensionalunitcellperformancemodel•in OpenFOAM© and include degradation

Develop correlations linking the catalyst layer structure •withmembraneelectrodeassembly(MEA)performanceand degradation

Develop Durability Windows•

Technical BarriersThisprojectaddressesthefollowingtechnicalbarriersof

theDOEFuelCellTechnologiesOfficeMulti-YearResearch,Development, and Demonstration Plan [1].

(A) Durability(ofthePtcatalystandPtcathodecatalystlayer)

(B) Performance

(C) Cost (indirect)

Technical TargetsInthisprojectfundamentalstudiesofthePt/carbon

catalyst degradation mechanisms and degradation rates are conducted and correlated with unit cell operational conditions and catalyst layer structure and composition. Furthermore, forwardpredictivemicroandmacromodelsforcathodeperformanceanddegradationarebeingdeveloped.Designcurves, generated both through model simulations and experimentalwork,willenableMEAdesignerstooptimizeperformance,durability,andcosttowardsthe2020targetsforfuelcellcommercialization[1]:

SystemDurability(10%performanceloss)•

Transportation applications: 5,000 hours –

Stationary applications (1-10 kW – e): 60,000 hours

Electrocatalyst (transportation applications) •

SupportStability:<10%massactivitylossafter –400 hrs @ 1.2 V in H2/N2

Effectivecatalystsurfacearea(ECSA)loss<40% –

Platinum-grademetaltotalloading:0.125mg/cm – 2

V.D.5 Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches

Wessel – Ballard Power SystemsV.D Fuel Cells / Degradation Studies

V–122DOE Hydrogen and Fuel Cells Program FY 2013 Annual Progress Report

FY 2013 AccomplishmentsIdentifiedthepreferredPtdissolutionsiteonaPt•crystalanchoredonacarbonsurfaceandextractedthetransport/diffusionratesofPtspeciesintheionomer

Predictedthelocaldistributionofeffectiveproperties•andidentifiedoxygen“storage”aspectsofionomericfilmsthroughtransientmicro-structuralcatalystmodelsimulations

DevelopedaPtdissolutionmodelformixedPtoxide•formationfromwaterandairforperformanceanddegradation prediction

BuilttheUnitCellModelinanopen-sourceplatform•thatallowsforcontinuedimprovementofthemodelinthe public domain.

Developedcorrelationsofbeginningoftest(BOT)and•endoftest(EOT)performancelossbreakdownwithcathode catalyst layer composition, morphology, material properties, and operational conditions

Identifieddesignwindowsandparameterswhicharekey•MEA design levers

Identifiedadesignflowpathofinteractionsfrom•materialspropertiesandcatalystlayereffectivepropertiestoperformancelossbreakdownforconditioned and degraded catalyst layers

G G G G G

IntroDuCtIonCatalyst/catalystlayerdegradationhasbeenidentifiedas

asubstantialcontributortofuelcellperformancedegradationandthiscontributionisexpectedtoincreaseasMEAsare driven to lower Pt loadings in order to meet the cost targetsforfull-scalecommercialization.Priortothestartofthisprojectsignificantprogresswasmadeinidentifyingcatalyst degradation mechanisms [2,3] and several key parametersthatgreatlyinfluencethedegradationrates,including electrode potentials, potential cycling, temperature, humidity, and reactant gas composition [2,4,5,6]. Despite these advancements, many gaps with respect to catalyst layer degradationandanunderstandingofitsdrivingmechanismsstillexisted.Inparticular,accelerationofthemechanismsunderdifferentfuelcelloperatingconditions,duetodifferentstructuralcompositions,andasafunctionofthedrivetolowerPtloadingswasanareanotwellunderstood.Inordertoclosethesegaps,thisprojectfocusedonunderstandingoftheeffectofoperatingconditionsandcathodecatalystlayer structure and composition on catalyst degradation mechanisms and degradation rates.

Theprojectobjectivewastodevelopforwardpredictivemodels and to conduct systematic cell degradation studies

thatenablequantificationofthecathodecatalystlayerdegradationmechanismsandratesandcorrelationofmaterialspropertiesasafunctionofkeyoperationalandstructural parameters.

APProACh Models have been developed at the molecular, micro-

structural, and macro-homogeneous scales that include degradationeffectsrelatedtoplatinumdissolution,transportandplating,carbonsurfaceoxidationandcorrosion,andionomerthinning/conductivityloss.Themodelsprovidetheabilitytostudytheeffectsofcomposition,themorphologicaldesign, and the operational window on catalyst degradation via simulated accelerated stress testing. The design curves generatedineachscaleofthemodelingworkenablethedevelopmentofmitigationstrategiesthroughtrade-offanalysis.

Acceleratedstresstestingcoupledwithstate-of-the-artinsitu/exsitucharacterizationtechniqueshavebeenusedtocorrelateMEAperformancelosswithstructuralchangesmeasured within the Pt cathode, as well as to develop key operationalandcatalyst/catalystlayerstructuraldegradationdesigncurves.Theexperimentalresultsalsoservedtoprovide model validation.

rESultS

Model Development

Effortswithinthisfiscalyearwerefocussedontheopen-source integration into OpenFOAM©, development ofthegraphicaluserinterface,thecompletionofworkontheplatinumoxidemodel,andtheinvestigationoftheeffectofplatinumloadingmasstransportlimitationsinthemicrostructural catalyst model.

Inordertosimulateplatinumdissolutionandplating,aplatinumoxidemodelcapableofpredictingtheoxidecoverageunderairandhydratedconditionswasrequired.Asnotedpreviously,literaturemodelsforthepredictionofoxidesunderairandhydratedconditionswerereadilyavailable,butwereonlyvalidatedforvoltagesbelowtheequilibriumopen-circuitvoltage(OCV)potentialofthecell.UponinvestigationitwasfoundthatthesemodelswerenotcapableofcapturingthegrowthofoxidesontheplatinumsurfaceforpotentialsabovetheOCV.Are-derivationandmodificationoftheexistingmodelswasundertakensuchthatkeychangesweremadeinthebehaviorofoxidegrowthandthedescriptionfortheavailabilityofactiveplatinumsites.Themodifiedandimprovedoxidemodel(Figure1B) shows substantially better predictive capability as comparedtotheoriginal(Figure1A)model.Inparticular,theabilityofthemodeltocapturetheoxidationpeakhasbeendramatically improved while the reduction peak still shows someroomforimprovementaroundthelocationoftheonset

V–123FY 2013 Annual Progress Report DOE Hydrogen and Fuel Cells Program

V.D Fuel Cells / Degradation StudiesWessel – Ballard Power Systems

potential.CouplingthemodifiedPtoxidemodeltotransportandoxygenreductionreactionkineticparametersintheintegrated MEA Degradation Model will properly capture the performanceintheoperatingrangeofthefuelcell.

Theeffectofplatinumloadingwasstudiedinthemicro-structural model by systematically increasing the overall loadingandprobingthespecifictransportphenomenawithinthecatalystmorphology.IneachcasethelocalKnudseneffects(Figure2A)wereaccountedfor,inadditiontotransportacrossandwithintheionomericfilms.Itwasfoundthattheoxygenconcentrationdroppedsubstantiallyasafunctionoftheincreasedcatalystlayerthickness(Figure2B)such that gas phase transport worsens as the thickness increases.Theeffectofthisthicknesschangeiscontraryto what is seen in regards to the polarization predictions (Figure 2C) in which there are additional losses related to

the gas phase transport. These polarization curves show a distinctlossduetoareductioninplatinumsurfacearea,butthelossofthisareaalsoincursasecondaryeffectrelatedtotheinterfacialareasbetweenionomerandplatinum.Thischangeintheinterfacialareaproducesaneffectwhichcanbedescribedviaashapefactorcorrectioninthelocaldiffusionandresultingconcentration(Figure2D).Thisshapefactorisapredictedplotfromthemicrostructuralsimulationsandshows clearly that the localized species transport resistance increasessignificantlyastheplatinumloadingisreduced.

The open-source model integration has been completed in OpenFOAM©andwillbefullyreleasedastheFC-PEMSimulation Package. The model has been implemented in a flexibledimensionalformatsuchthatone-,two-,andthree-dimensional simulations are possible. Further, the package hasagraphicaluserinterfaceinordertomanagecasefiles,runs,andmodificationofvariousrequireduserinputdata.Themodelusesfrontendmeshgenerators,calculationpackages,andpost-processingthatisfreelyavailableintheopen-source domain.

Experimental Parametric Studies

Effortswithinthisfiscalyearwerefocusedondeveloping(1)correlationsthatlinkMEAperformanceand degradation to catalyst layer composition, structure, componentproperties,andeffectivepropertiesand(2)designwindows.TheoverallmotivationwastoidentifyparameterswhicharekeyleversfortheMEAdesigner,andthatwouldallowthecatalystmanufacturertooptimizecatalystparametersforenhancedMEAperformanceanddurability. Figure 3A shows the approach taken in linking the catalyst carbon support and catalyst powder structure tothecatalystlayerstructure,effectiveproperties,andperformanceoftheMEA.ThisapproachaddressesbothBOTandEOTperformance;thelatterbeingcapturedviachangesinthecatalystlayerstructureandeffectivepropertieswithdegradation.ThedetailedinteractionsofthedifferentmeasurablesisshownonFigure3B.Whilemostoftheparameterswerequantified(greenboxes),theyellowandpalebluecolorshighlightthegapsinquantificationmethods,andthesearesubsequentlycalculatedbytheUnitCellModel.

Thereactiondistributioninthecatalystlayerisaffectedthroughbalancingofthedifferentover-potentialsinorderto minimize the total polarization losses. Thus, changes to onecatalystlayerpropertycanhaveanaffectoneachofthedifferentover-potentialsthatareinherentinthepolarizationcharacteristics.Forexample,masstransportlimitations,causedbyreduceddiffusivityorincreasedcatalystlayerthickness,willreducethelocaloxygenconcentrationatthecatalystsurfacecausinganincreaseinkineticlosses.Thisresultsinashiftofthereactiondistributioninthecatalystlayertoaccessmoreoxygen,thuscausingareductioninmasstransport losses and an associated increase in catalyst layer ionic loss. Similarly, proton conductivity, intrinsic kinetic

Figure 1. Cyclic voltammogram predictions using (A) the literature Pt-oxide model and (B) a re-derived, modified Pt-oxide model.

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5-4

-3

-2

-1

0

1

2x 10-4

Voltage vs RHE

Cur

rent

den

sity

(Am

p/cm

2 Pt)

Predicted CVExperimental

B

Predicted

Wessel – Ballard Power SystemsV.D Fuel Cells / Degradation Studies

V–124DOE Hydrogen and Fuel Cells Program FY 2013 Annual Progress Report

activity,andcatalystsurfaceareacanalsoaffectthereactiondistributionandpolarizationlosses.AnexampleoftheeffectofcatalystlayerthicknessisshowninFigure4.

Whileanincreaseincatalystlayerthicknessaffectsmasstransportlossesduetooxygendepletioneffects,catalystlayer ionic loss, caused by an increase in ionic resistance, was observed to be the dominant loss mechanism (Figure 4a).Inthisexample,thePtloadingwasheldconstant,andthethicknessincreasewasduetoalowerPt/Cratiowithinthe catalyst layer. For the thicker catalyst layers the current distributionisforcedfurtherintothecatalystlayertoaccessthesameamountofECSAasthethinnercatalystlayer.Asaresult,thethickercatalystlayerexhibitsahigherionicloss. With degradation (Figure 4A), the catalyst layer ionic lossincreasesduetoPtdepletionatthemembrane/catalystinterface(Figure4C)whichshiftsthereactionpenetrationfurtherintothecatalystlayer.Aneffectivethickness

(Figure4B)calculatedfromthecatalystlayerioniclossesandtheionicresistivityshowsthattheincreaseineffectivethickness(reactionpenetration)agreeswiththethicknessofthe Pt depleted region (~3 µmPtdepletionforthe9µm layer and 6-8 µmPtdepletionforthe31µm layer).

Durabilitywindowsweredevelopedforboththecatalystlayer structural design levers and operational conditions. Table 1 summarizes the time at the upper AST potential to reach15%performancelossatacurrentdensityof1.0A/cm2 foravarietyofoperationalparameters.Asshownbefore,theimpactoftheupperpotentiallimitismostsevere;under100% relative humidity (RH) conditions, the operational time is increased ~34 times by reducing the upper potential limitfrom1.4Vto1.0V.Theeffectoftemperatureislesssevereandinfactatlowerpotentials(≤1.2 V) when Pt dissolution is the dominant degradation mechanism, theeffectoftemperatureintherangefrom60to90°Cis

Figure 2. (A) Knudsen number for a catalyst morphology; platinum loading effect on (B) oxygen transport normalized depth profile, (C) catalyst polarization, and (D) the effective shape factor for oxygen transport.

(A) (B)

(C) (D)

V–125FY 2013 Annual Progress Report DOE Hydrogen and Fuel Cells Program

V.D Fuel Cells / Degradation StudiesWessel – Ballard Power Systems

Properties Catalyst Layer

Pt Loading

Pt DispersionPt Agglomerate

Size (Conditioned)

Surface Area (ECSA)

Kin

etic

Lo

ss

Catalyst and Ionomer

Dispersion

Carbon Aggregate

Size / Surface Area

Carbon / Pt Ratio

Catalyst powder (ECA)

Reactio

n D

istribu

tion

Catalyst LayerStructure

Carbon Support

StructureCatalyst Powder Structure

Pt/C Powder Pore Size Distribution /

Porosity

Ionomer Content

Catalyst Morphology,

Surface Species; XPS /

SEM

Catalyst Bulk Density

Ionomer

101

Diffusivity, O2

Perfo

rman

ce

102

Carbon Morphology,

Surface Species; XPS,

SEM 107

App. Activity (i0) / Tafel

Slope)

Intrinsic Activity (i0 /Tafel Slope)

Protonic Conductivity /

Resistivity

Pt Crystallite Orientation

Utilization

CL Pore Size Distribution /

Porosity

Tortuosity (pores, gas

phase)

Ionomer Bulk Conductivity

Tortuosity (ionomer)

CL Thickness

Carbon Aggregate Pore

Size Distribution /

Porosity

111

113

115

116

117

118

119

120

121

123130

131

132

133

135

139

142

114

151

CL Morphology, Surface Species

153

Ionomer Properties (EW,

Surface Energy, etc)

CL Uniformity (e.g. Cracks)

Ink Processing (Composition,

Mixing, Coating, Drying)

Water Saturation

159

Mass T

ran

spo

rt : K

inetic L

oss

Limiting Current

Ion

ic Lo

ss

CL R

esistance

138

140

Ionomer Volume Fraction

154

113

113

129

LegendQuantified Relationship

Expected Relationship (Quantification Gap)

Independent output parameter (not controlling in flow chart)

Expected Relationship (Water Saturation, Quant. Gap)

Measureable, Quantified

Measureable, Quantification Gap

Independent output parameter

Water Saturation, Quantification Gap

Hyperlink to Correlation Detailed Slides #

138

138

139

Figure 3. (A) Correlations approach flow chart. (B) Interactions and linkage of catalyst layer component characteristics, catalyst layer composition, structure, and effective properties and performance.

(A)

(B)

Nafion is a registered trademark of E.I. du Pont de Nemours and Company

Wessel – Ballard Power SystemsV.D Fuel Cells / Degradation Studies

V–126DOE Hydrogen and Fuel Cells Program FY 2013 Annual Progress Report

-5

0

5

10

15

20

25

30

35

0 10 20 30 40Thickness (micron)

CL

Ioni

c Lo

ss, 0

.5A

/cm

2(m

V)Pt/C Ratio Study BOTPt/C Ratio Study EOT

Pt DepletionEffect

A

0

2

4

6

8

10

12

0 10 20 30 40Thickness (micron)

Effe

ctiv

e Th

ickn

ess

, 0.5

A/c

m2

(mic

ron)

Pt/C Ratio Study BOTPt/C Ratio Study EOT

Pt Depletion Effect

B

Pt Depletion

EOTC

Figure 4. Catalyst layer ionic loss as a function of (A) measured catalyst layer thickness and (B) effective catalyst layer thickness (reaction penetration), (C) scanning electron micrograph of a degraded catalyst layer.

Table 1. Operational Durability Windows for the Baseline MEA (Pt50LSAC, 0.4 mg/cm2 cathode loading)

Operational Parameter Lower Level Lower Level Time to 15% Performance Loss

Upper Level Upper Level Time to 15% Performance Loss

UPL (100% RH, 80°C)

1.0 V 243 hours 1.4 V 7 hours

Temperature (100% RH, 1.4 V UPL)

60°C 46 hours 90°C 2.5 hours

Temperature (50% RH, 1.4 V UPL)

60°C 70 hours 90°C 5 hours

RH, cathode(1.4 V UPL, 80°C)

60% RH 11 hours 100% RH 8 hours

RH, cathode(1.2 V UPL, 80°C)

60% RH 1,500 hours 100% RH 200 hours

UPL - upper potential limit

V–127FY 2013 Annual Progress Report DOE Hydrogen and Fuel Cells Program

V.D Fuel Cells / Degradation StudiesWessel – Ballard Power Systems

abstract 222ndECSMeeting,Honolulu,Hawai’i,October7–12,2012.

3.G.Brunello,J.I.Choi,S.SJang,“DensityFunctionalTheoryStudyofPtDissolutionatWater-PtInterface”,submittedabstract222ndECSMeeting,Honolulu,Hawai’i,October7–12,2012.

4. V. Colbow, M. Dutta, A. Young, Z. Ahmad, D. Harvey, S.Wessel,“PerformanceDegradationandStructuralChangeswithPtCathodeCatalystlayerDesign”,submittedabstract222nd ECS Meeting,Honolulu,Hawai’i,October7–12,2012.

5. D.Harvey, A. Bellemare-Davis,K. Kunal, B. Jayansankar, J.Pharoah,V.Colbow,A.Young,S.Wessel,“StatisticalSimulationofthePerformanceDegradationofaPEMFCElectrodeAssembly”submitted abstract 222ndECSMeeting,Honolulu,Hawai’i,October7–12, 2012.

6. K. Artyushkova, P. Atanassov, M. Dutta, V. Colbow, S. Wessel, “Ex-situCharacterizationofDegradationMechanismofMEAsbyiImagingXPSandSEM”,submittedabstract222nd ECS Meeting, Honolulu,Hawai’i,October7–12,2012

7.S.A.Stacy,J.S.Allen,PercolationinCatalystLayerofPEMFC”,submitted abstract 222ndECSMeeting,Honolulu,Hawai’i,October7–12, 2012.

8.R.Shahbazian-Yassar,“MembraneElectrodeAssemblyDegradationinProtonExchangeMembraneFuelCells:AViewFromNanoscale”,InternationalConferencesofYoungResearcherson Advanced Materials, July 1–6, 2012, Singapore.

9.M.Khakaz-Baboli,D.A.Harvey,J.G.Pharoah,“Investigatingtheperformanceofcatalystlayermicro-structureswithdifferentplatinumloadings”,submittedabstract222nd ECS Meeting, Honolulu,Hawai’i,October7–12,2012.

10.S.Wessel,V.Colbow,M.Dutta,A.Young,D.Harvey,“TheimpactofMaterialsPropertiesandCathodeCatalystStructure/CompositiononMEAPerformanceandDurability”,HydrogenandFuel Cells 2013, Vancouver B.C., June 16–19, 2013.

11. D. Harvey, A. Bellemare-Davis, B. Jayasankar, K. Karan, J.Pharoah,A.Young,M.Dutta,V.Colbow,S.Wessel,“SimulationoftheORRMulti-pathwayandCatalystDissolutionforaPEMFC:TheEffectofSurfaceCoverageandASTcycling”,HydrogenandFuel Cells 2013, Vancouver B.C.,June 16–19, 2013.

12.S.Wessel,“WatermanagementinLowTemperaturePEMFuelCells,Industrieworkshop:WassermanagementinPEM-Brennstoffzellen,Freiburg(Germany),31January2013.

13. K. Artyushkova, P. Atanassov, M. Dutta, D. Harvey, V. Colbow,andS.Wessel,“StructuralCorrelations:DesignLeversforPerformanceandDurabilityofCatalystLayers”submittedabstract224th ECS Meeting, San Francisco, CA, October 27 – November 1, 2013.

rEFErEnCES 1.Hydrogen,FuelCells&InfrastructureTechnologiesProgram:Multi-YearResearch,DevelopmentandDemonstrationPlan,U.S.DepartmentofEnergy,EnergyEfficiencyandRenewableEnergy,2011revision.http://www.eere.energy.gov/hydrogenandfuelcells/mypp/

insignificant.However,carboncorrosionissubstantiallyaffectedbytemperatureandatanupperpotentiallimitof1.4V,anincreaseintemperaturefrom60to90°Creducestheoperational time ~18 times at 100% RH and 14% at 50% RH. Furthermore,changingtheRHfrom100%to50%atconstanttemperaturewillapproximatelydoubletheoperationaltimetoreach15%performanceloss.TheeffectofRHwasfoundtobemoresignificantforthePtdissolutionmechanism;a7.5xincreaseintimeto15%voltagelosscanbeachievedbyreducingthecathodeRHfrom100%to60%.

ConCluSIonS The overall conclusions are:

The lower corner and lower edge Pt atoms at the carbon •interfacewerefoundtobetheleaststableandassuchmost likely to dissolve.

ThediffusionratesforPtO• 2 and Pt(OH)2 species werefoundtobeverysimilarduetotheirsimilarsize(activationenergyofdiffusion:-13kJ/molforPt(OH)2, -11kJ/molforPtO2.

Oxygendissolutionmodeledwithinthecatalyststructure•showedthattheionomerfilmstendtobethinwithlittleresistance.

Theeffectofcatalystlayercompositiononlocal•conditions is observed through the variation in transport parameters, with decreasing platinum loading, the transport resistance increases due to an increased ‘localized’currentdemandandreducedionomericcontact area.

The correlations between materials properties, •composition,structure,andeffectivepropertiesofcathodecomponentsshowsimilartrendsforBOTandEOT MEAs.

Designwindowsrevealdurabilityaccelerationfactorsfor•various operational conditions.

Overall,thisworkhasprovidedsignificantadvancementsintheabilitytomodelanddesigndurablefuelcellproductsandtounderstandtheroleofcatalystlayermorphologyandstructureonthedurabilityoftheMEA.Theoutcomeofthisprojectissubsequentlyassistinginreducingtheiterativedesign/testcycleprocessfornextgenerationfuelcellproducts via model simulations.

FY 2013 PublICAtIonS/PrESEntAtIonS 1.G.Brunello,J.I.Choi,S.SJang,“Multi-scaleFirstPrincipleModelingofThree-PhaseSystemofPolymerElectrolytemembraneFuelcell”,submittedabstract222nd ECS Meeting, Honolulu, Hawai’i,October7–12,2012.

2.G.Brunello,J.I.Choi,S.SJang,“DensityFuncionalTheoryStudyandModeldevelopmentonPt-Nano-particles”,submitted

Wessel – Ballard Power SystemsV.D Fuel Cells / Degradation Studies

V–128DOE Hydrogen and Fuel Cells Program FY 2013 Annual Progress Report

4.Y.Shao,G.Yin,Y.Gao,UnderstandingandApproachesfortheDurabilityIssuesofPt-BasedCatalystsforPEMFuelCell.JournalofPowerSources2007,171,558-566.

5.M.S.Wilson,F.Garzon,K.E.Sickafus,S.Gottesfeld,SurfaceAreaLossofSupportedPlatinuminPolymerElectrolyteFuelCells.JournaloftheElectrochemicalSociety1993,140,2872-2876.

6.P.J.Ferreira,G.J.IaO’,Y.Shao-Horn,D.Morgan,R.Makharia,S.Kocha,H.Gasteiger,InstabilityofPt/CElectrocatalystsMembraneFuelCellsAMechanisticInvestigation.JournaloftheElectrochemical Society 2005, 152, A2256-A2271.

2.J.Wu,X.Z.Yuan,J.J.Martin,H.Wang,J.Zhang,J.Shen,S.Wu,W.Merida,AReviewofPEMFuelCellDurability:DegradationMechanismsandMitigationStrategies.JournalofPower Sources 184, 104-119.

3. R. Borup, J.P. Meyers, B. Pivovar, Y.S. Kim, R. Mukundan, N. Garland, D. Myers, M. Wilson, F. Garzon, D. Wood, P. Zelenay, K. More, K. Stroh, T. Zawodinski, J. Boncella, J.E. McGarth, M.Inaba,K.Miyatake,M.Hori,K.Ota,Z.Ogumi,S.Miyata,A.Nishikata,Z.Siroma,Y.Uchimoto,K.Yasuda,K.Kimijima,N.Iwashita,ScientificAspectsofPolymerElectrolyteFuelCell Durability and Degradation. Chemical Reviews 2007, 107, 3904-3951.