燃料电池(Low-Platinum Nanostructured Catalysts for Fuel Cells).ppt

KarenSwider-LyonsandPeterBouwmanNavalResearchLaboratoryWashington,DCWojtekDmowskiUniversityofTennesseeKnoxville,TN,Low-PlatinumNanostructuredCatalystsforFuelCells,U.S.TransportationOilDemand,Strategiesneededtoclosetheproduction/utilizationgapUsefuelcellstoincreaseefficiencyanddecreasefuelconsumption,Electricityfromelectrochemistry,ElectrochemicalconversionprocessOxygenandhydrogencombinedoncatalyststoproducewater,electricityandheat,,,,,electrolyte,anode,cathode,,H,O22H2e-H2O,H22H2e-,,,load,,,e-,e-,,,,,H,H,ProtonexchangemembranefuelcellPerfluorosulfonicacidNafionpolymermembrane,Ptcatalysts,,,Resistivelossesduetomaterialsandinefficientreactions.,Hydrocarbonsashydrogensource,LogisticsfuelRichestsourceofhydrogenMustbereedtohydrogenSulfur,nitrogenandCO2maybesequestered,refinery,OIL,H2,H2,H2,H2,H2,H2,H2,H2,,reer,,Hydrogenfromwaterelectrolysisisexpensiveduetohighmaterialsandenergycostsofelectrolyzers,Storagetanks,,,SO2CO2,,Fuelcell,EnvironmentalIssueswithPlatinum,FromTheLonminGroupwebsite,MiningPtcreatesalotofwasteInfuelcellera,attentiontowardenvironmentallyfriendlyminingandrecycling,EPAAdvantagesoflowPtcatalysts,LoweringPtwilllowerthecostoffuelcellsIntroducefuelcellsmorebroadlytoconsumermarketLowerfuelconsumptionLessPlatinumusedLessPtminedandrecycledLesschemicalwaste,Apossiblesolutiontotheproblem,,TraditionalapproachMakeandtestnewplatinum“alloys”ChangecatalystmicrostructureOurapproachDesignphase-segregated,mixedconductingnanocompositesforRAPIDTRANSPORTofchemicalspecies,,Alloycompositions,Transitionmetals,nanocompositephases,,,,,,Nanocompositephasesarestilllargelyunexplored-duetodifficultyintheircharacterization,,FocusonloweringPtinfuelcellcathodeCathodehasmostPtbecauseslowoxygenreductionkineticspoorPtstabilityandripeningovertime.,SupportPtonametaloxideandimproveopportunityfor*protonmobilitytoPtsites*chem/physattractionofO2*metal-supportinteractionswithPt,LowPtcatalystsforfuelcells,Catalystdevelopmentviaelectrochemicalandstructuralanalysis,Pt-MOxsystems,1.Pt-FePOxxH2O-hydrousironphosphateIronphosphateusedasananti-corrosionadditiveinpaintFePOxisapartialoxidationcatalystUnderintensescrutinyasaLi-ionbatterycathode2.Pt-SnOxxH2O-hydroustinoxidePriorORRliteratureshowspromiseforanhydrousPt-SnOxTinhydratesarecorrosionresistant,HydrousoxidesareexcellentforprotonconductionSelectedoxideshaveotheridealcatalyticpropertiese.g.partialoxidationMaterialshaveopenframeworkstructures,“OpenFrameworkInorganicMaterials”A.K.CheethamG.Frey,T.Loiseau,Angew.Chem.1999,v.38p.3286.,ExampleMicroporousAlPO4,Pt-FePOx/VulcanCasORRcatalysts,Pt-FePO4catalystshavehigherORRactivitythanPt/carbonstandard,,UserotatingdiskelectrodeexperimentstocompareoxygenreductionactivityofnewcatalyststostandardcatalystsCriticalfactorsElectrodepreparationTestingconditions0.1MHClO41600rpm60CComparetotheoreticalvaluesforPt,9Pt-FePOxyH2O50VC,20Pt-VC,FePOxCyclicVoltammetry,FePOxhasnoactivityfortheORR9wtPt-FePOxishighlyactivefortheORR,FePOx/VC,9Pt-FePOx/VC,0.1MHClO41600rpm60C,StructureoftheactivePt-FeOsampleisglassyinconventionalelectronmicroscopyandX-raydiffraction,ConventionalX-raydiffraction,TEM,StructureofPt-FePOxElectrocatalysts,AtomicpairdistributionfunctionPDF,X-rayorneutronscatteringisFourier-transedtogivedistributionofinter-atomicdistancesinarealspace.,Highenergy,highintensitysourcesareessentialtominimizeerrorsandimprovestatistics.,,PDFanalysis,,SQ,,XRDlargelyamorphous,Short-rangeorder,s,StructureofPt-FePOxwithPDFanalysis,Ironphosphateberlinite–a-quartzstructure,PDFanalysisofhigh-energyXRDshowsorderedmediumrangestructureMicroporousstructurefacilitateshighprotonicconductionPtservesasaglass-modifierandopensporesforaccessFe2/Fe3mixedvalencestatesforhighcatalyticactivity,Nextsteps,ReduceparticlesizeofoxidestoimproveelectricalpropertiesofFePOx,VCimpregnatedwithPt-FePOx,Solution-filteredPt-FePOx,Effectofparticlesize,SmallernanoparticlesizeleadstoHigherelectronicconductivitytunnelingfromcarbonHighersurfaceareamoresitesforcatalysis,Pt-FePOxmixedwithVulcancarbonvs.Pt-FePOximpregnatedonVulcancarbon,Fuelcellsareefficientfuelconversionsystemsthatmayleadtosignificantfuelsavings-lesspollutionLowergreenhousegasesatacentralfuelreingsiteandhydrogenstoredinfueltanksNanomaterialsmaybeusefulroutestoloweringPtcontentoffuelcellsandloweringtheircostNewanalyticaltechniquesmaybeneededfortheaccuratestudyofnewnanomaterials,SummaryandOutlook,Acknowledgements,DepartmentofEnergy,EEREOfficeofNavalResearchThesynchrotronexperimentswerecarriedoutattheNSLS-BrookhavenNationalLab,