简介：AnAu/ceria(0.44%,massfraction)catalystcontaininggoldionswaspreparedbyamodifieddepositionprecipitationmethod,andtheevolutionofgoldionsinthecatalystanditsinfluenceonthecatalysisofCOoxidationwereinvestigated.Itwasfoundthattheas-preparedcatalystcontaininggoldionswithhighvalencecouldfullyoxidizeCOat–10°CinitiallybutwasdeactivatedgraduallyatlowtemperaturesduringthereactionwithCOortreatmentbyunpurifiedair.ThedeactivationofthecatalystduringCOoxidationortreatmentofitbyunpurifiedairwasindependentandprogressiveatlowtemperatureswhiletheactivityofthecatalystatrelativelyhightemperatureswasmaintainedwell.DuringthereactionwithCOortreatmentbyunpurifiedair,theXPSresultsindicatethatgoldspeciesevolvedfromhighvalencetolowvalenceandthediffusereflectanceUV-Visspectrashowthathighvalencegoldwasreducedtochargedgoldclusters,goldclustersgrewtosmallgoldcrystalsandsmallgoldcrystalsgrewtolargegoldparticles.Accordingly,thehighvalencegoldcorrespondedtotheactivityatlowtemperaturesandthemetallicgoldwasactiveandrelativelystableathightemperatures.Theturnoverfrequencies(TOF)ofthecatalyststreatedbydifferentmethodsat273Kdecreasedwiththeevolutionofgoldspeciesfromhighvalencetolowvalence,nomaximumofTOFwasobservedalthoughgoldparticlesinthecatalystattainedtoabout2―3nmduringthetreatment.AnAu/ceriacatalystwithagoldloadof0.87%(massfraction)maintainedagoodactivityforCOoxidationwithin18hatroomtemperature.Thecatalystswerecharacterizedviatransmittedelectronicmicroscopy(TEM),inductivelycoupledplasmaopticalemissionspectrometry(ICP-OES),X-raydiffraction(XRD)andBETspecificsurfaceareaandUV-VisDRSaswell.

简介：HighactiveandstablegoldcatalystssupportedoncrystallineFe2O3andCeO2/Fe2O3werepreparedviathedeposition-precipitationmethod.ThecatalystwithaAuloadof1.0%calcinedat180°CshowedaCOconversionof100%at-8.9°C,whileAu/CeO2/Fe2O3convertedCOcompletelyat-16.1°C.Evenhavingbeencalcinedat500°C,Au/Fe2O3stillexhibitedsignificantcatalyticactivity,achievingfullconversionofCOat61.6°C.ThecatalystwithalowAuloadof0.5%couldconvertCOcompletelyatroomtemperatureandkepttheactivityunchangedforatleast150h.N2adsorption-desorptionmeasurementsshowthatthecrystallinesupportspossessedahighspecificsurfaceareaofabout200m2/g.CharacterizationsofX-raydiffractionandtransmissionelectronmicroscopyindicatethatgoldspecieswerehighlydispersedasnanoorsub-nanoparticlesonthesupports.Evenafterthecatalystwascalcinedat500°C,theAuparticlesremainedinanano-sizeofabout6―10nm.X-rayphotoelectronspectrarevealthatthesupportedAuexistedinmetallicstateAu0.ThemodificationofAu/Fe2O3byCeO2provedtobebeneficialtotheinhibitionofcrystallizationofFe2O3andthestabilizationofgoldparticlesindispersedstate,consequentlypromotingcatalyticactivity.