Direct water splitting under visible light with nanostructured hematite and WO3 photoanodes and a GaInP2 photocathode

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1、JournalofTheElectrochemicalSociety,1555F91-F962008F910013-4651/2008/1555/F91/6/$23.00©TheElectrochemicalSocietyDirectWaterSplittingunderVisibleLightwithNanostructuredHematiteandWO3PhotoanodesandaGaInP2Photocathode,zHeliWang,*ToddDeutsch,**andJohnA.Turner*NationalRenewableEnergy

2、Laboratory,Golden,Colorado80401,USAAp-GaInP2photocathodewaspairedwithnanostructuredhematiteandtungstentrioxidephotoanodestoinvestigatetheutilityofthesesystemsfordirectwatersplittingundervisiblelightillumination.Forthehematitesystem,underilluminationatopen-circuitconditions,thepotenti

3、alofhematiteshiftscathodicallyandthatoftheGaInP2shiftsanodically.Undershort-circuitconditionandvisiblelightillumination,thecombinationofthetwophotoelectrodescansplitwater,thoughwithaverylowrateofafew
A/cm2evenatanintensityof1W/cm2.Itwasdeterminedthattheverylowphotocurrentfromthehemat

4、itenanorodphotoelectrodelimitstheshort-circuitcurrentofthetwo-photoelectrodecombination.Similarpotentialshiftswereobservedwiththenanostruc-turedWO/GaInPcombination.However,atlightintensitiesbelow0.2W/cm2,theshort-circuitedcombinationwouldnotsplit32waterduetoaninsufÞcientpotentialdiff

5、erence.Above0.2W/cm2,thecombinationcansplitwaterundervisiblelight,with
20
A/cm2obtainedat1W/cm2.AlinearphotocurrentÐlightintensityrelationshipwasobservedandwasattributedtoefÞcientchargetransferandalowrecombinationofthechargecarriers.ThebandgapandtheassociatedabsorptionlimitofWO3remai

6、nachallengeforahigherefÞciencysystem.©2008TheElectrochemicalSociety.
DOI:10.1149/1.2888477Allrightsreserved.ManuscriptsubmittedDecember14,2007;revisedmanuscriptreceivedJanuary30,2008.AvailableelectronicallyMarch12,2008.SinceFujishimaandHondaÞrstdemonstrateddirectwatersplit-bandgapSC

7、usuallyoxidestoformlowerbandstates,allowing14,5tingatachemicallybiasedTiO2electrode,thephotoelectrochemi-somepartofthevisiblespectratobeused.calproductionofhydrogenandoxygenfromwaterhasreceivedAnapproachtomakeupforenergeticmismatchistobiasthe2-9photoelectrode.Onewaytoprovideabiasis

8、viaamultijun