ARTICLEBehaviorCharacterizationofHydrogenSpeciesonZnOElectrodeduringElec-trolyticReductionofWaterLufengYuan,WangyangLi,GuangyuanXu,MengqiWan,ZhenZhang*KeyLaboratoryofSurfaceandInterfaceChemistryandEnergyCatalysisofAnhuiHigherEducationInsti-tutes,andDepartmentofChemicalPhysics,UniversityofScienceandTechnologyofChina,Hefei230026,China(Dated:ReceivedonJune17,2022;AcceptedonJuly27,2022)ThebehaviorofhydrogenproductiononZnOelec-trodeduringtheelectrolyt-icreductionofwaterwasin-vestigatedbycyclicvoltam-metry(CV)andcathodepolarizationexperimentscombinedwithinsituRa-manandphotolumines-cencespectroscopy.CVex-perimentsindicatethathy-drogenspeciespreferstodiffuseintotheZnObulkatnegativepotentialsandoccupiesoxygenvacanciesandinterstitialsites.Meanwhile,theH2Oreductionisself-enhancedduringtheelectroreductionprocess,asevidencedbythetracecrossingoftheCVcurvesandthechronoamperometricexperiment.TheinfluenceoftheHspeciesontheZnOelectrodeduringtheelectrocatalyticprocesseswascharacterizedbytheinsituRamanandphotoluminescencespectroscopies.Theseresultshelpustounderstandthehydrogen-relatedcatalyticorelectro-catalyticprocessesonZnOsurfaces.Keywords:Electrocatalysis,ZnO,Waterreduction,InterstitialhydrogenI.INTRODUCTIONZincoxide(ZnO)isasemiconductormaterialwithadirectbandgapof3.37eVaswellasalargeexcitonbindingenergyof60meVatroomtemperature[1,2].Duetoitsexcellentpropertiesincludinghighelectronmobility,goodthermalstability,earthabundanceandlowcost,ZnOhasawideapplicationprospectinthefieldsofcatalysis[3],conductivefilms[4],solarcells[5],gassensors[6],photodetectors[7],andluminescentde-vices[8].Thedefects,suchasoxygenvacancy(VO),intersti-tialZn(Zni),Znvacancy(VZn),andevenhydrogenspecies,cansignificantlyaffecttheelectricalandopti-calpropertiesofZnO[9−11].HydrogenisanalmostubiquitousimpurityinZnO.TheinteractionbetweenhydrogenandZnOplaysimportantrolesinenergycon-versionreactions,suchassyngasconversionreactionorhydrogenevolutionreaction(HER)[3,12−14].Asearlyasthe1950s,Thomasetal.haveobservedthatth...
