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1、赵赵宇宇 黄子健黄子健 王宏宇王宏宇20162016年年1111月月2323日日Photo-catalysts for water splittingcontents1、Basic principles and developing history 2、Strategies to improve the photocatalytic activity3、The outlooks of the photocatalytic materials firstdiscoveryandbasicprinciplesFirstdiscoveredat1972initiatedbythedemonstrat
2、ionofphoto-electrochemical(PEC)well-knownastheHonda-Fujishimaeffectfirstdiscoveryandbasicprinciplesenergybandtheoryfull-occupiedhalf-occupiedunoccupiedbandgapCBVBdifferentenergylevelscorrespondwithdifferentbandssemi-conductorsareveryusefulinthisareaK. Maeda / Journal of Photochemistry and Photobiolo
3、gy C: Photochemistry Reviews 12 (2011) 237268 firstdiscoveryandbasicprinciplesHalf-reactions using sacrificial electron donors and acceptors Half-reactions using sacrificial electron donors and acceptors testreactionsforoverallwatersplittingtestreactionsforoverallwatersplittingfirstdiscoveryandbasic
4、principlesspecificneedsthatmustbemetspecificneedsthatmustbemet1 1、thebandgaprestrictionthebandgaprestriction2 2、migratewithoutrecombinationmigratewithoutrecombination3 3、inhibitthebackwardreactioninhibitthebackwardreactionK. Maeda / Journal of Photochemistry and Photobiology C: Photochemistry Review
5、s 12 (2011) 237268 generallytobeparticlesexample:Pt-TiO2at1980withNaOHloadedonthecocatalystfirstdiscoveryandbasicprinciplesmajor developing historyspecialstructuresthewell-knownlamellarparticlemajor developing historyspecialstructuresperovskitesCubicPerovskitesDoublePerovskitesmajor developing histo
6、ryAurivilliusphasesDion-JacobsonphasesRuddleson-Popperphasesspecialstructuresperovskitesmajor developing historyamazingeffectsofthenetworkofoctahedralunitsofmetalcationsprobablyfromitsuniqueelectronicpropertiesspecialstructuresperovskitesmajor developing historyspecialstructures：RuddlesdenPoppertype
7、layeredperovskitesofA2La2Ti3O1032 T.Takata,K.Shinohara,A.Tanaka,M.Hara,J.N.Kondo,K.Domen,J.Photochem. Photobiol. A: Chem. 106 (1997) 45.aseriesoflayeredperovskiteshaveAQYshigherthan20%underUVirradiationmajor developing historyspecialstructuresperovskites:tunnelstructuredBaTi4O9andNa2Ti6O9built-inpol
8、arizationfieldpentagonalprismtunnel26 Y. Inoue, T. Niiyama, Y. Asai, K. Sato, J. Chem. Soc., Chem. Commun. (1992) 579.major developing historyspecialelectronicstructuresd10-Typemetaloxidesthepoorsymmetryofoctahedralandtetrahedralcoordinationthepoorsymmetryofoctahedralandtetrahedralcoordinationtendst
9、oleadtotheformationofisolatedorbitalstendstoleadtotheformationofisolatedorbitalslocalinternalfieldsduetothedipolemomentinsidethedistortedunitslocalinternalfieldsduetothedipolemomentinsidethedistortedunitsMGa2O4specialelectronicstructuresd10-TypemetaloxidesGa2O3hybridizeds,porbitalshavealargedispersi
10、on,leadingtoincreasehybridizeds,porbitalshavealargedispersion,leadingtoincreasemobilityofphotogeneratedelectronsintheconductionbandmobilityofphotogeneratedelectronsintheconductionbandmajor developing historyspecialelectronicstructuresmixed-configurationmetaloxideshybridizationoftheatomicorbitalsofth
11、etwometalionsshowhybridizationoftheatomicorbitalsofthetwometalionsshoweffectonthedensityofstatesandenergydispersionintheconductionbandseffectonthedensityofstatesandenergydispersionintheconductionbandsincreasethemobilityofphotoexcitedelectronsandholesincreasethemobilityofphotoexcitedelectronsandholes
12、major developing historydevelopmentofvisiblelightutilizationmajor developing historyprovidesadiscreetenergyleveltotallynewbandmajor developing historydevelopmentofvisiblelightutilization-valencebandcontrolmajor developing historydevelopmentofvisiblelightutilizationSpectralsensitizationorganicdyesori
13、norganicnarrow-gapsemiconductorsenergygapsufficientlysmalltoharvestvisiblephotonsenergygapsufficientlysmalltoharvestvisiblephotonsexcited-statepotentialthatismorenegativeexcited-statepotentialthatismorenegativethebiggestproblemisthebackelectrontransferthebiggestproblemisthebackelectrontransfermajor
14、developing historydevelopmentofvisiblelightutilizationSpectralsensitizationslowelectrontransferfromthenanoparticulateIrOslowelectrontransferfromthenanoparticulateIrO22catalysttotheoxidizeddyecatalysttotheoxidizeddyewhichdoesnotcompeteeffectivelywithbackelectrontransferfromtheconductionbandofwhichdoe
15、snotcompeteeffectivelywithbackelectrontransferfromtheconductionbandofTiOTiO22tothedyetothedyemajor developing historymetal-freephotocatalystselectrontransitionsfromthevalencebandpopulatedbyN2porbitalselectrontransitionsfromthevalencebandpopulatedbyN2porbitalstotheconductionbandformedbyC2porbitalstot
16、heconductionbandformedbyC2porbitalsmajor developing historyWatersplittingthroughtwo-stepphotoexcitation(Z-scheme)controllingcontrolling the selectivity for the forward reactions on each photocatalystmajor developing historyWatersplittingthroughtwo-stepphotoexcitation(Z-scheme)Strategytoimprovethepho
17、tocatalyticactivityWays to improve photocatalytic activity Improving the physicochemical properties of the photocatalyst Refining cocatalysts Controlling the reaction conditionsStrategytoimprovethephotocatalyticactivity A Tradeoff Asmallsizeincreasesthedensityofsurfacecatalyticsitesincreasetheprobab
18、ilityofrecombinationbetweenphotogeneratedelectronsandholes,StrategytoimprovethephotocatalyticactivityOriginal picture had some small mistakes. We have correct them.StrategytoimprovethephotocatalyticactivityShape or form of a photocatalystMesoporous transition-metal oxidesNomura and Domen et al., rep
19、orted that a mesoporous tantalum oxide, prepared by a ligand-assisted templating method, functions as a photocatalyst capable of splitting water into H2 and O2 under UV irradiation ( 200 nm), when modified with an NiOx cocatalyst.This high activity appears to be due to the thin walls of the mesopore
20、s, which provide a short distance for the excited electrons and holes to travel to the surface, reducing the probability of electronhole recombination.StrategytoimprovethephotocatalyticactivityShape or form of a photocatalystSchematicillustrationStrategytoimprovethephotocatalyticactivityShape or for
21、m of a photocatalystTransition-metal oxide nanosheetsThese compounds consist of negatively charged corner- and/or edge-shared MO6(M = Ti, Nb, Ta) octahedral units that stack to form a two-dimensional layered structure interleaved with alkaline cations to compensate for the negative charge of the she
22、ets. Upon photoexcitation, electrons and holes are generated in the sheets, causing redox reactions with reactant molecules adjacent to the layers.StrategytoimprovethephotocatalyticactivityShape or form of a photocatalystStrategytoimprovethephotocatalyticactivityShape or form of a photocatalystDopin
23、g a photocatalyst with foreign elements can change its physicochemical properties such as particle size, surface morphology, and band structure, depending on the dopant. Doping with foreign elementsNiO-loaded NaTaO3 is highly active for photocatalytic water splitting under UV irradiation , Kato and
24、Kudo successfully enhanced the water splitting rate by 23 times by doping with lanthanides.StrategytoimprovethephotocatalyticactivityShape or form of a photocatalystStrategytoimprovethephotocatalyticactivityCocatalysts for the promotion of surface reactionsStrategytoimprovethephotocatalyticactivityC
25、ocatalysts for the promotion of surface reactionsTwo methods of introducing cocatalysts Impregnation methodproper precursor species are impregnated with a photocatalyst, followed by thermal annealing to produce a desired form of cocatalyst.In situ photochemical depositionnanoparticles of metals (e.g
26、., Pt, Pd) can be prepared by irradiation of an aqueous solution containing a semiconductor powder (e.g., TiO2, WO3), metal ions, and an electron donor StrategytoimprovethephotocatalyticactivityThe polymerized complex (PC) methodThis method consists of two essential steps:(1)incorporation of inorgan
27、ic precursors in a polymer resin with molecular-level dispersion(2) subsequent calcination to eliminate the polymer and produce a crystalline metal oxide. StrategytoimprovethephotocatalyticactivityThe polymerized complex (PC) methodStrategytoimprovethephotocatalyticactivityCocatalysts for the promot
28、ion of surface reactionsGeneral role of cocatalysts in photocatalytic water splittingStrategytoimprovethephotocatalyticactivityCocatalysts for the promotion of surface reactionspH=3.0pH=4.5pH=6.2Reaction pH and electrolyte in the reactant solutionStrategytoimprovethephotocatalyticactivityCocatalysts
29、 for the promotion of surface reactionsTraditional cocatalysts for water splittingTheoutlooksofthephotocatalyticmaterialsLa-andRh-codopedSrTiO3Mo-dopedBiVO4asolar-to-hydrogenenergyconversionefficiencyof1.1%+TheoutlooksofthephotocatalyticmaterialsTheoutlooksofthephotocatalyticmaterialsCr2O3and-TiO2ST
30、Hreached33%at419nmand1.1%,respectively,at331Kand10kPa.Fe3+/2+redoxcouplesexhibitedanAQYof4.2%at420nmandanSTHof0.1%underthebestreactionconditions.VSTheoutlooksofthephotocatalyticmaterialsScreenPrintingAphotocatalystsheetpreparedbyscreenprintinganinkcontainingSrTiO3:La,Rh,BiVO4:Mo,andaAucolloidexhibit
31、edanSTHof0.1%.TheoutlooksofthephotocatalyticmaterialsSemiconductors?CoordinationPolymers!Theoutlooksofthephotocatalyticmaterials2010,Garciaandco-workers，ZrcontainingMOFs(UiO-66)，2.4mLH2，3hours2014,Xueandco-workers，ErythrosinB&UiO-66system，recyclableTheoutlooksofthephotocatalyticmaterials2013,Xuetal.
32、，insertingplatinumsaltwithintheframeworkTheoutlooksofthephotocatalyticmaterialsZhangandcoworkersreportedthecombinationofCdS,reducedgrapheneoxide(RGO)andUiO-66intoacompositesystem:13.8mmol/gCdS*hMuchhigherthanCdS:1.0mmol/gCdS*hEvenhigherthanPt/CdS(consideredthemostactive)Theoutlooksofthephotocatalyti
33、cmaterialsAnareaof250,000km2,correspondingto1%oftheearthsdesertarea,wouldberequiredtoprovideone-thirdoftheprojectedenergyneedsofhumansocietyin2050fromsolarenergyAcknowledgementsThe convenience provided by the web of science.The research of many great scientistsThe field that is very interestingThanks for your attention!
