An Efficient Visible-Light-Sensitive Fe(III)-Grafted TiO2 Ph

An Efficient Visible-Light-Sensitive Fe(III)-Grafted TiO2 Photocatalyst

J.Phys.Chem.C2010,114,16481–1648716481

AnEf cientVisible-Light-SensitiveFe(III)-GraftedTiO2Photocatalyst

HuogenYu, HiroshiIrie,*, YoshikiShimodaira,§YasuhiroHosogi,|YasushiKuroda,|MasahiroMiyauchi,⊥andKazuhitoHashimoto*, ,#

ResearchCenterforAdVancedScienceandTechnology(RCAST),TheUniVersityofTokyo,4-6-1Komaba,Meguro-ku,Tokyo153-8904,Japan,CleanEnergyResearchCenter,UniVersityofYamanashi,4-3-11Takeda,Kofu,

Yamanashi400-8511,Japan,CorporateR&DCenter,ShowaDenkoK.K.,1-1-1Ohnodai,Midori-ku,Chiba,Chiba

267-0056,Japan,ShowaTitaniumCo.,Ltd,3-1Nishinomiya-machi,Toyama,Toyama931-8577,Japan,NationalInstituteofAdVancedIndustrialScienceandTechnology,TsukubaCentral5,1-1-1Higashi,Tsukuba,Ibaraki305-8565,Japan,andDepartmentofAppliedChemistry,TheUniVersityofTokyo,7-3-1Hongo,Bunkyo-ku,Tokyo113-8656,JapanReceiVed:May14,2010;ReVisedManuscriptReceiVed:August15,2010

WehavepreparedaTiO2-basednovelvisible-light-sensitivephotocatalyst,inwhichFe(III)speciesweregraftedonarutileTiO2surface(denotedasFe(III)/TiO2).WithuseofX-rayabsorption nestructureanalysis,thegraftedironspeciesweredeterminedtobeinthe3+stateandadoptanamorphousFeO(OH)-likestructure.Fe(III)/TiO2displayedopticalabsorptioninthevisiblelightrangeover400nm,whichwasassignedtotheinterfacialchargetransferfromthevalencebandofTiO2tothesurfaceFe(III)species.Itsphotocatalyticactivitywasevaluatedbythedecompositionofgaseous2-propanolundervisiblelight(400-530nm),whichrevealedahighquantumef ciency(QE)of22%.Monochromaticlightexperimentsindicatedthattheeffectivewavelengthregionwasextendedasfaras580nmwhilemaintainingaQEofgreaterthan10%.OnthebasisoftheanalogytoCu(II)-graftedTiO2photocatalyst(Irie,H.;etal.Chem.Phys.Lett.2008,457,202),wespeculatethatthehighperformanceofthepresentphotocatalystisderivedfromthephotoproducedholesthataregeneratedinthevalencebandofTiO2andcontributetotheoxidativedecompositionof2-propanol,andthecatalyticreductionofoxygen(presumablymultielectronreduction)byphotoproducedFe(II)speciesonTiO2.

Introduction

TiO2photocatalystshavebeeninvestigatedformanyyearswiththeaimofincreasingtheirsensitivitytovisiblelightinordertoutilizeincominglightenergymoreef ciently.Thedopingofvariousanions(N,S,C,etc.)1,2andcations(Cr,V,Fe,Mn,Co,Ni,etc.)3intothelatticeofTiO2hasbeenfoundtoextenditsabsorptionintothevisiblelightregion.MostdopedTiO2photocatalystsaresensitivetovisiblelightduetotheformationofalocalizednarrowbandabovethevalenceband(VB)ofTiO2thatoriginatesfromthedopantcationsandanions.However,thesephotocatalyststypicallyexhibitaloweractivityundervisiblelightthanunderUVlightbecausetheoxidationpowerandmobilityofphotoge-neratedholesinthelocalizednarrowbandarelessthanthoseintheVBofTiO2.2aOnthebasisoftheseproperties,weassumedthatthedopingofforeignelementsintoTiO2isnotaneffectivestrategyfordevelopinghighlyef cientTiO2photocatalystssensitivetovisiblelight,andotherapproachesarethereforenecessary.

Oneofthepromisingapproachestowardincreasingtheef ciencyofTiO2asaphotocatalystisso-calleddye-sensitization.Forexample,itiswell-knownthatRucomplex-*Towhomcorrespondenceshouldbeaddressed.H.I.:phone+81-55-220-8092,fax+81-55-220-8092,e-mailhirie@yamanashi.ac.jp.K.H.:phone+81-3-5452-5080,fax+81-3-5452-5084,e-mailhashimoto@light.t.u-tokyo.ac.jp.

CleanEnergyResearchCenter,TheUniversityofTokyo.

UniversityofYamanashi.§

CorporateR&DCenter,ShowaDenkoK.K.|

ShowaTitaniumCo.,Ltd.⊥

NationalInstituteofAdvancedIndustrialScienceandTechnology.#

DepartmentofAppliedChemistry,TheUniversityofTokyo.

modi edTiO2showsvisiblelightabsorption.Inthissystem,uponexcitationoftheRucomplex,anelectronintheexcitedstateissubsequentlyinjectedintotheconductionband(CB)ofTiO2.4a-cAnotherexampleofdye-sensitizationistheH2[PtCl6](orPtCl4)-modi edTiO2system,4d,ereportedbyKischetal.,4dthatinvolvesvisiblelightabsorptionbyPt(IV)-chloridetogeneratetwonewredoxcenters,anoxidativeCl/Cl-pairandareductivePt(IV)/Pt(III)pair.Pt(III)returnstoPt(IV)byinjectingelectronsintotheCBinTiO2,whileClreturnstoCl-throughtheoxidizationoforganiccompounds.Inbothcases,theelectrontransfertoTiO2proceedsviatheexcitedstateoftheadsorbedmolecules.

WiththeexceptionofTiO2-basedmaterials,somereportshaveexaminedoxidematerialsthataresensitivetovisiblelightfortheoxidativedecompositionoforganiccompounds,5amongwhichAg3PO4wasreportedveryrecently.5e

Recently,wereportedthatTiO2powderswithgraftedmetalions(Cu(II),Cr(III),andCe(III))6-8werecapableofservingasphotocatalystssensitivetovisiblelight.Asthermaltreatmentwasnotperformed,theseionsmayexistonlyonthesurfaceofTiO2andwouldnotbedopedintothelattices.ThegraftingofCu(II)toformCu(II)/TiO2resultedinaquantumef ciency(QE)for2-propanoldecompositionundervisiblelight(>450nm)thatwasratherhigh(QE)8.8%).7Inthissystem,itisassumedthatvisiblelightinitiatesinterfacialchargetransfer(IFCT),i.e.,electronsintheVBofTiO2directlytransfertoCu(II),notviatheexcitedstate,toformCu(I)whileholesremainintheVBofTiO2basedonthesuggestionsbyCreutzetal.9relatingtophotoinducedIFCTbetweenthecontinuousanddiscreteenergylevelsofsolidsandsurface-associatedmolecularspecies,respectively.TheholesproducedintheVBofTiO2decompose

10.1021/jp1071956 2010AmericanChemicalSociety

PublishedonWeb09/01/2010

An Efficient Visible-Light-Sensitive Fe(III)-Grafted TiO2 Photocatalyst

16482J.Phys.Chem.C,Vol.114,No.39,2010organicsubstancesresultinginthehighactivityofthisphoto-catalyst,whileCu(I)producedbyelectrontransferispresumedtoreduceadsorbedO2andtherebyconsumeelectrons.7AlthoughtheQEoftheCu(II)/TiO2undervisiblelightirradiationwashigherthanthatoftypicalN-dopedTiO2,aphotocatalystcurrentlybeingintensivelyinvestigatedbyseveralresearchgroups,thereisaneedtofurtherdevelopandimprovevisiblelight-activeTiO2systemsforuseinpracticalapplications.Here,weattemptedtoidentifyanewmetalionthatcouldbeusedinplaceofCu(II)towardimprovingthephotocatalyticactivityofT …… 此处隐藏：31531字，全部文档内容请下载后查看。喜欢就下载吧 ……