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TiO2wasmodifiedwithrareearthcerium(Ce)andthencoatedonindiumtinoxide(ITO)conductiveglasssubstrate.Thecoatedsubstratewassinteredat450℃for30minandsemiconductorworkingelectrodewasobtained.Cyclicvoltammetry(CV)testsindicatethatwhenthepolarizationpotentialiswithintherangeof＋1.35-＋4.0V(vs.SCE),thereliesoxidationreactionpeaksontheCVcurve,whichcorrespondtotworeactions:[Ce3+O22-]defect-＋h+→[Ce4+O22-]andOH-＋h+→OH;thesetworeactionsarebothhole(h+)consumptiveandarecompetitivetoeachother.Sincetheformeriseasiertooccur,theexcitedholes(h+)takeprecedencetorecombinewith[Ce3+O22-]defect-ratherthanmigratingtothesemiconductorsurface,andconsequently[Ce3+O22-]defect-＋h+→[Ce4+O22-]isthemajorreaction,whilethereactionOH-＋h+→OHishardtooccur.Withinthepolarizationpotentialrangeof－0.8-～－1.2V,thereliesthereductionreactionofO2＋e-→O2-,whichisthereactionbetweentheexcitedelectrons(e-)thathavemigratedtothematerialsurfaceandtheoxygenadsorbedonthematerialsurface.Electronspinresonance(ESR)testsindicatethatthereareveryweakOHsignalsonlyunderUVirradiationswhileconsiderableO2-signalsarecapturedunderanyofdark,visiblelightandUVirradiation;thistestresultisinfullyagreementwiththeelectrochemicalanalysisresults. |
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