碳纳米材料增强二氧化钛光催化剂

ReviewCarbonaceousnanomaterialsfortheenhancementofTiO2photocatalysisRowanLeary,AidanWestwood*InstituteforMaterialsResearch,UniversityofLeeds,Leeds,LS29JT,UKARTICLEINFOArticlehistory:Received28July2010Accepted8October2010Availableonline15October2010ABSTRACTSemiconductorphotocatalysishasimportantapplicationssuchasachievingsustainableenergygenerationandtreatingenvironmentalpollution.TiO2hasbeenthemostwidely-researchedphotocatalyst,butsuffersfromlowefficiencyandnarrowlightresponserange.CombiningTiO2withcarbonaceousnanomaterialsisbeingincreasinglyinvestigatedasameanstoincreasephotocatalyticactivity,anddemonstrationsofenhancementareplenti-ful.Thisreviewsurveystheliteratureandhighlightsrecentprogressinthedevelopmentofnanocarbon-TiO2photocatalysts,coveringactivatedcarbon,carbondoping,carbonnano-tubes,[60]-fullerenes,graphene,thinlayercarboncoating,nanometriccarbonblackandmorerecentlydevelopedmorphologies.Mechanismsofenhancement,synthesisroutesandfutureapplicationsaresummarisedanddiscussed.Newinsightandenhancedphoto-catalyticactivitymaybeprovidedbynovelnanocarbon-TiO2systems.Ongoingchallengesandpossiblenewdirectionsareoutlined.2010ElsevierLtd.Allrightsreserved.Contents1.Introduction...................................................................................7422.Basesofphotocatalyticenhancement...............................................................7433.CarbonaceousnanomaterialsfortheenhancementofTiO2photocatalysis..................................7443.1.Synthesistechniquesfornanocarbon-TiO2photocatalysts.........................................7443.2.Relativephotocatalyticactivity...............................................................7453.3.Activatedcarbonphotocatalystsupports.......................................................7463.4.Carbon-dopedTiO2........................................................................7473.5.CNT–TiO2composites......................................................................7503.6.[60]-Fullerene-TiO2composites...............................................................7563.7.Graphene-TiO2composites..................................................................7583.8.Othernanocarbon-TiO2composites...........................................................7594.Applications...................................................................................7615.Discussionandfutureperspectives.................................................................7626.Conclusions...................................................................................7630008-6223/$-seefrontmatter2010ElsevierLtd.Allrightsreserved.doi:10.1016/j.carbon.2010.10.010*Correspondingauthor:Fax:[phone].E-mailaddress:[e-mail](A.Westwood).CARBON49(2011)741–772availableatficientphotocatalyticprocesseshavethepotentialtoyieldmajorstepsforwardintacklingsomeofsociety’sgreatestchallenges;mostprominentlyinmeetingcleanenergydemandandtacklingenvironmentalpollution.Thedevelop-mentofeffectivesemiconductorphotocatalystshasthereforeemergedintooneofthemostimportantgoalsinmaterialsscience.Indeed,sincethefirstdemonstrationofphotocata-lyticwatersplittingonatitaniumdioxide(TiO2)electrodebyFujishimaandHonda[1],thelevelofresearchinthefieldhasgrownatanexponentialrate(Fig.1a).Asimilarlydramaticriseininteresthasoccurredsincethemid-1990swithregardstocarbonaceousnanomaterials(Fig.1b)becauseoftheiruniqueproperties,andthepotentialtocontrolthesepropertiesthroughstructuralandcomposi-tionalmodification.Inthepastdecadethesetwofieldsofinteresthavecometogether,withsignificantattentionnowbeingdevotedtoexploringtherolethatcarbonaceousnanomaterialsmayplayinphotocatalyticprocesses(Fig.1c).Photocatalysisapplicationsofwidereachingimportanceincludewatersplittingforhydrogengeneration[2–8],degrada-tionofenvironmentalpollutantsinaqueouscontaminationandwastewatertreatment[9–17],carbondioxideremediation[18],self-cleaningactivity[19–21]andairpurification[15,22,23].Anidealphotocatalyticmaterialwouldcombinehighactivityregardingtherelevantprocessofinterestwithhighefficiencyofsolarenergyconversion.Itshouldalsobenon-toxic,biologicallyandchemicallyinert,stableoverlongperiods,readilyavailableandeasilyprocessable.However,nomaterialorsystemcurrentlyexiststhatsatisfiesalltheserequirements.Indeed,althoughthepowerdeliveredtotheEarthfromtheSun(around1.5·105terawatts[24])dwarfsallthatavailablefromotherenergysources–renewableandnon-renewable–andgreatlyexceedsthatconsumedbyhumancivilisation(around13terawatts[24]),onlyafractionofthisen-ergyisharvestedbycurrentphotocatalyticmaterials,whichtypicallyhavesolarphotoconversionefficienciesof5%.Byfarthemostresearched