質(zhì)子交換膜燃料電池氧電極有序穩(wěn)定結(jié)構(gòu)的構(gòu)筑及耐久性研究摘要

質(zhì)子交換膜燃料電池是目前最為成熟的可再生能源轉(zhuǎn)化裝置，其氧還原反應(yīng)（ORR）是電極反應(yīng)的重要環(huán)節(jié)。然而，質(zhì)子交換膜燃料電池中氧還原反應(yīng)的影響因素較多，導(dǎo)致其效率和耐久性不盡如人意。本文圍繞質(zhì)子交換膜燃料電池氧電極的有序穩(wěn)定結(jié)構(gòu)，從結(jié)構(gòu)優(yōu)化及穩(wěn)定性角度，開展了一系列的研究。首先，探究了有序結(jié)構(gòu)對ORR的催化作用及電化學(xué)性能的影響，發(fā)現(xiàn)超晶格納米孔結(jié)構(gòu)的氧電極具有較好的活性和穩(wěn)定性。同時，研究了材料表面的交換作用對燃料電池性能的影響，發(fā)現(xiàn)表面功能化可以有效提高氧電極的催化性能。最后，分析了氧電極在長時間運(yùn)行過程中的耐久性問題和降解機(jī)理，并提出相應(yīng)解決方案。

關(guān)鍵詞：質(zhì)子交換膜燃料電池；氧還原反應(yīng)；有序穩(wěn)定結(jié)構(gòu)；納米孔；表面功能化；耐久性

Abstract

Protonexchangemembranefuelcell(PEMFC)iscurrentlythemostmaturerenewableenergyconversiondevice,andoxygenreductionreaction(ORR)isanimportantpartofelectrodereactionsinPEMFC.However,thefactorsaffectingtheORRinPEMFCsarediverse,leadingtopoorefficiencyanddurability.ThispaperfocusesontheorderedstablestructureoftheoxygenelectrodeinPEMFCsandconductsaseriesofstudiesfromtheperspectivesofstructuraloptimizationandstability.Firstly,weinvestigatedthecatalyticeffectoforderedstructuresonORRandtheelectrochemicalperformance,andfoundthattheoxygenelectrodewithsuperlatticenanoporousstructurehasgoodactivityandstability.Simultaneously,theeffectofsurfaceexchangeontheperformanceoffuelcellswasstudied,anditwasfoundthatsurfacefunctionalizationcaneffectivelyimprovethecatalyticperformanceoftheoxygenelectrode.Finally,thedurabilityproblemanddegradationmechanismoftheoxygenelectrodeduringlong-termoperationwereanalyzed,andcorrespondingsolutionswereproposed.

Keywords:protonexchangemembranefuelcell;oxygenreductionreaction;orderedstablestructure;nanopore;surfacefunctionalization;durabilitProtonexchangemembranefuelcells(PEMFCs)havebeenrecognizedasapromisinggreenenergytechnologyduetotheirhighenergyconversionefficiency,lowoperatingtemperature,andzero-emissionnature.However,thesluggishkineticsoftheoxygenreductionreaction(ORR)atthecathodeisstillalimitingfactorfortheircommercialization.

OneeffectivestrategytoenhancetheORRperformanceistoengineerthecathodecatalystlayerwithanorderedstablestructurefeaturinghighsurfaceareaanduniformporesizedistribution.Forinstance,theuseofmesoporouscarbonmaterialssuchasSBA-15andMCM-41asasupportforplatinum(Pt)catalysthasbeenreportedtosignificantlypromotetheORRkineticsbyfacilitatingoxygendiffusionandminimizingmasstransportlimitations[1].

AnotherapproachtoimprovetheORRactivityistofunctionalizethesurfaceoftheelectrocatalystwithcertaingroupsthatcanfacilitatetheadsorptionanddissociationofoxygenspecies.Forexample,nitrogen-dopedcarbonhasbeenusedasapromisingalternativetoPtduetoitshighstabilityandexcellentORRperformance,whichcanbeattributedtothechemisorptionofoxygenonthenitrogen-dopedsites[2].

Besides,thelong-termdurabilityofthePEMFCcathodeisofgreatconcern,astheORRprocesscanbeaccompaniedbytheformationofreactiveoxygenspeciesthatcausedegradationofthecatalystlayer.Tomitigatethisissue,somestrategieshavebeenproposed,suchasoptimizingthewatermanagementtopreventmembranedehydration,reducingtheoperatingtemperaturetominimizetheriskofcarboncorrosion,andapplyingprotectivecoatingstoimprovetheoxidativestabilityofthecatalystlayer[3].

Inconclusion,theORRperformanceofPEMFCcathodescanbeimprovedbytailoringthecatalyststructureandsurfacechemistry.Meanwhile,acomprehensiveunderstandingofthedegradationmechanismsandcorrespondingmitigationmeasuresisalsocrucialforthesustainableoperationofthefuelcellsystemOnepotentialapproachtofurtherimprovetheORRperformanceofPEMFCcathodesistoenhancethemasstransportofreactantsandproductswithintheelectrode.Thiscanbeachievedbyoptimizingtheelectrodemicrostructure,suchastheparticlesize,porosity,andtortuosity,aswellastheionomercontentanddistribution.Forinstance,increasingtheionomercontentcanimprovetheprotonconductivitywithintheelectrode,leadingtoenhancedelectrochemicalactivityanddurability[25].Moreover,theuseofnanostructuredcatalysts,suchasPt-basednanoparticles,canincreasetheactivesurfaceareaandfacilitatemasstransportbyreducingthediffusionlengthofreactantsandproducts[26].However,carefulcontroloftheparticlesizeanddistributionisnecessarytopreventagglomerationanddeactivationofthecatalyst[27].

AnothercrucialaspectofPEMFCcathodedesignistheintegrationwithothercomponentsofthefuelcellsystem,particularlythemembraneandanode.BecausetheORRreactionatthecathodeconsumesprotonandelectroncarriersgeneratedbythehydrogenoxidationreactionattheanode,theperformanceanddurabilityofthecathodearecloselycoupledwiththoseoftheanode.Therefore,optimizingtheanodecatalystandmicrostructure,aswellasthemembraneproperties,cansignificantlyimpacttheoverallfuelcellperformance[28,29].Forinstance,usingPtRualloyastheanodecatalystcanenhanceitsactivityandselectivitytowardshydrogenoxidation,whilemaintainingagoodCOtolerance[30].Additionally,increasingthemembranethicknessandreducingitsresistancecanimprovetheionicconductivityandreducethecrossoverofreactantgases,leadingtoenhancedcathodeperformance[31].

Overall,thedevelopmentofhigh-performanceanddurablePEMFCcathodesrequiresamultidisciplinaryapproachthatintegratesmaterialsscience,electrochemistry,transportphenomena,andsystemengineering.WhilesignificantprogresshasbeenmadeinunderstandingtheORRmechanism,optimizingthecatalyststructureandsurfacechemistry,andmitigatingdegradation,therearestillmanychallengesandopportunitiesforfutureresearch.Forinstance,thedevelopmentoflow-costandabundantnon-noblemetalcatalysts,aswellastheexplorationofnewmaterialsforthecatalystsupportandmembrane,canfurtherimprovetheperformanceandsustainabilityofPEMFCs.Theintegrationofadvancedmodelingandsimulationtools,suchasmultiscaleandmultiphysicsmodeling,canalsoenhanceourunderstandingofthecomplexanddynamicprocessesoccurringinPEMFCs,andfacilitatethedesignandoptimizationofthecathodeandothercomponents.Ultimately,thesuccessfulcommercializationofPEMFCsdependsonthebalanceofvariousfactors,suchasperformance,durability,cost,safety,andscalability,andthealignmentoftechnologicalinnovationwithsocialandenvironmentalneedsInadditiontoaddressingtechnicalchallenges,thewidespreaddeploymentofPEMFCsalsorequiresovercomingvariousnon-technicalbarriers.Onesuchbarrieristhelackofinfrastructureforproducing,storing,anddistributinghydrogenfuel,whichisnecessarytopowerPEMFCs.Currently,hydrogenismainlyproducedfromnaturalgas,butthereareeffortstodeveloprenewableandsustainablesourcesofhydrogen,suchaselectrolysisofwaterusingrenewableelectricityorbiomassgasification.However,thelowenergydensityandhighcostofhydrogenstorageanddistributionremainmajorchallengesthatneedtobeaddressed.

Anotherbarrieristheperceptionoffuelcellsasexoticandunfamiliartechnology,whichcancreateuncertaintyandriskforpotentialinvestorsandcustomers.Therefore,effortsareneededtoincreasepublicawarenessandunderstandingoffuelcellsandtheirbenefits,suchasreducedemissions,improvedenergysecurity,andeconomicdevelopment.Moreover,publicpoliciesandregulationscanplayacriticalroleincreatingasupportiveenvironmentforfuelcells,suchasbyprovidingincentivesandfundingforresearch,development,anddeployment,andbycreatingstandardsandcodesforsafetyandperformance.

Furthermore,thedeploymentofPEMFCsalsoraisesethicalandsocialissues,suchasthepotentialdisruptionofexistingenergysystemsandthedistributionofbenefitsandrisksamongdifferentstakeholders.Forexample,thetransitionfromfossilfuelstohydrogen-basedenergysystemscouldaffectthelivelihoodsofworkersandcommunitiesthatdependonthefossilfuelindustry.Therefore,ajustandequitabletransitionrequiresaddressingtheseissuesandengagingdiversestakeholders,suchasworkers,communities,andenvironmentalgroups.

Inconclusion,thedevelopmentanddeploymentofPEMFCsrequireamultidisciplinaryandintegratedapproachthataddressestechnical,environmental,social,andethicalaspects.WhilesignificantprogresshasbeenmadeinimprovingtheperformanceanddurabilityofPEMFCs,numerouschallengesremainthatrequirefurtherresearchanddevelopment.Moreover,thesuccessfulcommercializationofPEMFCsdependsoncreatingasu