光解水催化劑介紹photocatalysts

趙宇黃子健王宏宇2016年11月23日Photo-catalystsforwatersplittingcontents1、Basicprinciplesanddevelopinghistory2、Strategies

toimprovethephotocatalyticactivity3、TheoutlooksofthephotocatalyticmaterialsfirstdiscoveryandbasicprinciplesFirstdiscoveredat1972initiatedbythedemonstrationofphoto-electrochemical(PEC)well-knownastheHonda-Fujishimaeffectfirstdiscoveryandbasicprinciplesenergybandtheoryfull-occupiedhalf-occupiedunoccupiedbandgapCBVBdifferentenergylevelscorrespondwithdifferentbandssemi-conductorsareveryusefulinthisareaK.Maeda/JournalofPhotochemistryandPhotobiologyC:PhotochemistryReviews12(2011)237–268firstdiscoveryandbasicprinciplesHalf-reactionsusingsacrificialelectrondonorsandacceptorstestreactionsforoverallwatersplittingfirstdiscoveryandbasicprinciplesspecificneedsthatmustbemet1、thebandgaprestriction2、migratewithoutrecombination3、inhibitthebackwardreactionK.Maeda/JournalofPhotochemistryandPhotobiologyC:PhotochemistryReviews12(2011)237–268generallytobeparticlesexample:Pt-TiO2at1980withNaOHloadedonthecocatalystfirstdiscoveryandbasicprinciplesmajordevelopinghistoryspecialstructures—thewell-knownlamellarparticlemajordevelopinghistoryspecialstructures—perovskitesCubicPerovskitesDoublePerovskitesmajordevelopinghistoryAurivilliusphasesDion-JacobsonphasesRuddleson-Popperphasesspecialstructures—perovskitesmajordevelopinghistoryamazingeffectsofthenetworkofoctahedralunitsofmetalcationsprobablyfromitsuniqueelectronicpropertiesspecialstructures—perovskitesmajordevelopinghistoryspecialstructures：Ruddlesden–PoppertypelayeredperovskitesofA2La2Ti3O10[32]T.Takata,K.Shinohara,A.Tanaka,M.Hara,J.N.Kondo,K.Domen,J.Photochem.Photobiol.A:Chem.106(1997)45.aseriesoflayeredperovskiteshaveAQYshigherthan20%underUVirradiationmajordevelopinghistoryspecialstructures—perovskites:tunnelstructuredBaTi4O9andNa2Ti6O9

built-inpolarizationfieldpentagonalprismtunnel[26]Y.Inoue,T.Niiyama,Y.Asai,K.Sato,J.Chem.Soc.,Chem.Commun.(1992)579.majordevelopinghistoryspecialelectronicstructures—d10-TypemetaloxidesthepoorsymmetryofoctahedralandtetrahedralcoordinationtendstoleadtotheformationofisolatedorbitalslocalinternalfieldsduetothedipolemomentinsidethedistortedunitsMGa2O4specialelectronicstructures—d10-TypemetaloxidesGa2O3hybridizeds,porbitalshavealargedispersion,leadingtoincreasemobilityofphotogeneratedelectronsintheconductionbandmajordevelopinghistoryspecialelectronicstructures—mixed-configurationmetaloxideshybridizationoftheatomicorbitalsofthetwometalionsshoweffectonthedensityofstatesandenergydispersionintheconductionbandsincreasethemobilityofphotoexcitedelectronsandholesmajordevelopinghistorydevelopmentofvisiblelightutilizationmajordevelopinghistoryprovidesadiscreetenergyleveltotallynewbandmajordevelopinghistorydevelopmentofvisiblelightutilization-valencebandcontrolmajordevelopinghistorydevelopmentofvisiblelightutilization—Spectralsensitizationorganicdyesorinorganicnarrow-gapsemiconductorsenergygapsufficientlysmalltoharvestvisiblephotonsexcited-statepotentialthatismorenegativethebiggestproblemisthebackelectrontransfermajordevelopinghistorydevelopmentofvisiblelightutilization—SpectralsensitizationslowelectrontransferfromthenanoparticulateIrO2catalysttotheoxidizeddyewhichdoesnotcompeteeffectivelywithbackelectrontransferfromtheconductionbandofTiO2tothedyemajordevelopinghistorymetal-freephotocatalystselectrontransitionsfromthevalencebandpopulatedbyN2porbitalstotheconductionbandformedbyC2porbitalsmajordevelopinghistoryWatersplittingthroughtwo-stepphotoexcitation(Z-scheme)controllingtheselectivityfortheforwardreactionsoneachphotocatalystmajordevelopinghistoryWatersplittingthroughtwo-stepphotoexcitation(Z-scheme)StrategytoimprovethephotocatalyticactivityWaystoimprove

photocatalyticactivity

ImprovingthephysicochemicalpropertiesofthephotocatalystRefiningcocatalystsControllingthereactionconditionsStrategytoimprovethephotocatalyticactivityATradeoffAsmallsizeincreasesthedensityofsurfacecatalyticsitesincreasetheprobabilityofrecombinationbetweenphotogeneratedelectronsandholes,StrategytoimprovethephotocatalyticactivityOriginalpicturehadsomesmallmistakes.Wehavecorrectthem.StrategytoimprovethephotocatalyticactivityShapeorformofaphotocatalystMesoporoustransition-metaloxidesNomuraandDomenetal.,reportedthatamesoporoustantalumoxide,preparedbyaligand-assistedtemplatingmethod,functionsasaphotocatalystcapableofsplittingwaterintoH2andO2underUVirradiation(">200nm),whenmodifiedwithanNiOxcocatalyst.Thishighactivityappearstobeduetothethinwallsofthemesopores,whichprovideashortdistancefortheexcitedelectronsandholestotraveltothesurface,reducingtheprobabilityofelectron–holerecombination.StrategytoimprovethephotocatalyticactivityShapeorformofaphotocatalystSchematicillustrationStrategytoimprovethephotocatalyticactivityShapeorformofaphotocatalystTransition-metaloxidenanosheetsThesecompoundsconsistofnegativelychargedcorner-and/oredge-sharedMO6(M=Ti,Nb,Ta)octahedralunitsthatstacktoformatwo-dimensionallayeredstructureinterleavedwithalkalinecationstocompensateforthenegativechargeofthesheets.Uponphotoexcitation,electronsandholesaregeneratedinthesheets,causingredoxreactionswithreactantmoleculesadjacenttothelayers.StrategytoimprovethephotocatalyticactivityShapeorformofaphotocatalystStrategytoimprovethephotocatalyticactivityShapeorformofaphotocatalystDopingaphotocatalystwithforeignelementscanchangeitsphysicochemicalpropertiessuchasparticlesize,surfacemorphology,andbandstructure,dependingonthedopant.DopingwithforeignelementsNiO-loadedNaTaO3ishighlyactiveforphotocatalyticwatersplittingunderUVirradiation,KatoandKudosuccessfullyenhancedthewatersplittingrateby2–3timesbydopingwithlanthanides.StrategytoimprovethephotocatalyticactivityShapeorformofaphotocatalystStrategytoimprovethephotocatalyticactivityCocatalystsforthepromotionofsurfacereactionsStrategytoimprovethephotocatalyticactivityCocatalystsforthepromotionofsurfacereactionsTwomethodsof

introducingcocatalystsImpregnationmethodproperprecursorspeciesareimpregnatedwithaphotocatalyst,followedbythermalannealingtoproduceadesiredformofcocatalyst.

Insituphotochemicaldepositionnanoparticlesofmetals(e.g.,Pt,Pd)canbepreparedbyirradiationofanaqueoussolutioncontainingasemiconductorpowder(e.g.,TiO2,WO3),metalions,andanelectrondonor

StrategytoimprovethephotocatalyticactivityThepolymerizedcomplex(PC)methodThismethodconsistsoftwoessentialsteps:(1)incorporationofinorganicprecursorsinapolymerresinwithmolecular-leveldispersion(2)subsequentcalcinationtoeliminatethepolymerandproduceacrystallinemetaloxide.StrategytoimprovethephotocatalyticactivityThepolymerizedcomplex(PC)methodStrategytoimprovethephotocatalyticactivityCocatalystsforthepromotionofsurfacereactionsGeneralroleofcocatalystsinphotocatalyticwatersplittingStrategytoimprovethephotocatalyticactivityCocatalystsforthepromotionofsurfacereactionspH=3.0pH=4.5pH=6.2ReactionpHandelectrolyteinthereactantsolutionStrategytoimprovethephotocatalyticactivityCocatalystsforthepromotionofsurfacereactionsTraditionalcocatalystsforwatersplittingTheoutlooksofthephotocatalyticmaterialsLa-andRh-codopedSrTiO3Mo-dopedBiVO4asolar-to-hydrogenenergyconversionefficiencyof1.1%+TheoutlooksofthephotocatalyticmaterialsTheoutlooksofthephotocatalyticmaterialsCr2O3andα-TiO2STHreached33%at419nmand1.1%,respectively,at331Kand10kPa.Fe3+/2+redoxcouplesexhibitedanAQYof4.2%at420nmandanSTHof0.1%underthebestreactionconditions.VSTheoutlooksofthephotocatalyticmaterialsScreenPrintingAphotocatalystsheetpreparedbyscreenprintinganinkcontainingSrTiO3:La,Rh,BiVO4:Mo,andaAucolloidexhibitedanSTHof0.1%.TheoutlooksofthephotocatalyticmaterialsSemiconductors?CoordinationPoly