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1PaperReview李俊乾化学工程（专）14102932Synthesis,characterizationandelectrochemicalstudiesofnano-structuredCaWO4asplatinumsupportforoxygenreductionreaction(纳米钨酸钙的合成、表征和其负载铂对氧还原反应的电催化)2Literaturesource3ContentsIntroduction12Experimentalsection1Conclusions234Resultsanddiscussion41.IntroductionInrecentyears,protonexchangemembranefuelcells(PEMFCs)havebeenrecognizedaspromisingdevicesforportableandtransportapplicationsduetotheirgoodenergyconversionefficiency,highpowerdensity,lowoperatingtemperature,andeasytransport.PEMFC’Sworkingprinciple:51.IntroductionThecathodicreactionofoxygenreductionreaction(ORR)TheanodicreactionofhydrogenoxidationreactionforH2+2M→2MH2MH→2M+2H++2e-O2+H++M+e-→MHO2MHO2+H++e-→MO+H2OMO+H++e-→MOHMOH+H++e-→M+H2OElectrocatalyticreactionmechanism:6Inthefuelcellintheworkprocess,theplatinumcatalystactivesurfaceareawillbegraduallyreduced,resultingintheattenuationoffuelcellperformance.MCatalystsCarbonSubstrateO24H+H2O4e-O22H+2e-H2O2CO2H2OM流失(a)H2O2腐蚀载体MCatalystsCarbonSubstrateO22H+H2O2O22H+2e-H2O2CO2H2OM流失M-O,M-OH2e-(b)Oads、OHads中间物种使M表面钝化失活MCatalystsCarbonSubstrateH2SSO2M流失Poisoning(d)毒性物种使M中毒失活NO2COMCatalystsCarbonSubstrateM流失Magglomeratedordissolutionandreduction(c)催化剂的团聚、溶解、还原thepropertiesofPt/PtMalloyrecessionschematicdiagram7Experimentalsection282.ExperimentalsectionSynthesisofnanostructuredCaWO4:80°CpH=7whiteprecipitateswerecollectedbycentrifugationNa2WO42H2O(5mM)CaCl26H2O(5mM)CaWO4mixedtogetherdriedinitiallyatroomtemperaturecalcinate500Cfor5h92.Experimentalsection•Catalystpreparation:calciumtungstate(1)Graphite(2)CaWO4/graphiteelectrodeK2PtCl4（2.5mM）H2SO4（0.25M）thecatalystofPt/CaWO4-graphite30wt.%ofn-eicosaneheatedelectrochemicallyprecipitated1023Resultsanddiscussion113.ResultsanddiscussionTheapproximatecrystallitesizesofsampleswereestimatedbytheScherrer’sformula:TheparticlesizeandmorphologyofCaWO4wereexaminedusingTEM，D=10–25nm.coskD123.ResultsanddiscussionThesereductionpeaksarenotsymmetricbecauseofdepletionofPtCl42-ionsinthevicinityoftheelectrodesinpotentialsmorenegativethanthepeakpotentials.CyclicvoltammogramsduringelectrodepositionPtonbothgraphiteandnano-CaWO4/graphite.133.Resultsanddiscussion(a)and(b)ScanningelectronmicroscopyimagesofPt/CaWO4-graphite.Inthesepictures,brighterareascorrespondedtoPtandCaWO4thattheplatinumparticlesaredispersedoverthesurfaceofthesupportandgraphitesheet.143.Resultsanddiscussion(d)TheEDXspectrumpresenceofPt,CaandWinthePt/CaWO4-graphitecatalysts153.ResultsanddiscussionAreaindicatingthatelectrochemicalactivity.CyclicvoltammogramsofCaWO4-graphite,graphite,Pt/CaWO4-graphiteandPt/graphiteina0.5MH2SO4aqueoussolutionatscanrateof50mV/s.ThesizeoftheoxidationandreductioncurrentdependsonthevalueofPt-dispersion.163.Resultsanddiscussion返回Theoxygenreductionpeakcurrentincreaseslinearlywiththesquarerootofscanrate,emphasizingonthecontrollingofthereactionbyoxygendiffusiontotheelectrodesurfaceCyclicvoltammogramsofthePt/CaWO4-graphiteina0.5MH2SO4atvariousscanrates.173.ResultsanddiscussionThemorepositivehalfwavepotentialindicatestheenhancedelectroc-atalyticactivityofthecatalystsforORR.LinearsweepingvoltammogramsofPt/CaWO4-graphiteandPt/graphiteinO2saturated0.5MH2SO4solutionwithascanrateof25mV/s.183.ResultsanddiscussionItisclearthatthePt/CaWO4-graphiteshowsalowercharge-transferresistanceduetothesmallersemicircle’sdiametercomparedtoPt/graphitecatalystin0.5MH2SO4solution.NyquistplotforPt/CaWO4-graphiteandPt/graphitein0.5MH2SO4vs.Ag/AgCl.19Conclusions4204.conclusionsNano-structuredcalciumtungstatewassynthesizedbytheco-precipitation.TheapplicationofCaWO4asacatalystsupportforPt.Pt/CaWO4-graphitecatalystexhibitedbetterelectrochemicalactivityforoxygenreductionreactioninH2SO4solutiocomparedtoPt/graphite.21Thankyouforyourattention!