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1、MechanismofHydrogenEvolutionReactionon1T-MoS2fromFirstPrinciplesQingTang,andDe-enJiangACSCataL,JustAcceptedManuscriptDOI:10.1021/acscatal.6b01211PublicationDate(Web):20Jun2016Downloadedfromhttp:/pubs.acs.orgonJune26,2016JustAcceptedACSPublicationsuJustAcceptedmanuscriptshavebeenpeer-reviewedandaccep
2、tedforpublication.Theyarepostedonlinepriortotechnicalediting,formattingforpublicationandauthorproofing.TheAmericanChemicalSocietyprovidesMJustAccepted*asafreeservicetotheresearchcommunitytoexpeditethedisseminationofscientificmaterialassoonaspossibleafteracceptance.*JustAcceptedmanuscriptsappearinful
3、linPDFformataccompaniedbyanHTMLabstract.4,JustAcceptedmanuscriptshavebeenfullypeerreviewed,butshouldnotbeconsideredtheofficialversionofrecord.TheyareaccessibletoallreadersandcitablebytheDigitalObjectIdentifier(DOI).JustAcceptedisanoptionalserviceofferedtoauthors.Therefore,theJustAcceptedWebsitemayno
4、tincludeallarticlesthatwillbepublishedinthejournal.Afteramanuscriptistechnicallyeditedandformatted,itwillberemovedfromthe“JustAcceptedWebsiteandpublishedasanASAParticle.Notethattechnicaleditingmayintroduceminorchangestothemanuscripttextand/orgraphicswhichcouldaffectcontent,andalllegaldisclaimersande
5、thicalguidelinesthatapplytothejournalpertain.ACScannotbeheldresponsibleforerrorsorconsequencesarisingfromtheuseofinformationcontainedintheseJustAccepted”manuscripts.ACSCatalysisispublishedbytheAmericanChemicalSociety.1155SixteenthStreetN.W.Washington.DC20036PublishedbyAmericanChemicalSociety.Copyrig
6、htAmericanChemicalSociety.However,nocopyrightclaimismadetooriginalU.S.Governmentworks,orworksproducedbyemployeesofanyCommonwealthrealmCrowngovernmentinthecourseoftheirduties.36373839404142434445464748495051Therefore,AGhcanberewrittenasAGn=AEh+0.26,where0.26eVisacorrectionconstant.(a)AOJJOUUJLL(5一cae
7、waFigureI.Calculateddifferentialfreeenergyofhydrogenadsorption(AGh)asafunctionofhydrogencoverageonIT-M0S2surfaceinvacuum.3. Resultsanddiscussiono3.1Gibbsfreeenergy(AGh)ofatomichydrogenonthesurfaceandtheoptimalcoverage.91011 AGhofatomichydrogenadsorbedonacatalystisconsideredasagooddescriptorofHER1212
8、 activity.61AnoptimumHERactivitycanbeachievedatavalueofAGhclosetozero(Gh0),15indicatingthatthefreeenergyofadsorbedHisclosetothatofthereactantorproduct.Lower161718 AGhwillleadtostrongbondingtoadsorbedhydrogen,whilehigherAGhwillmaketheprotons19bondedtooweaklytothecatalystsurface,bothleadingtoslowHERki
9、netics.Thecalculatedfree20 energyAGhasafunctionofsurfaceHcoverageintheabsenceofwaterandabiaspotentialis2324showninFigure1.TheadsorptiongeometriesatdifferentHcoveragewereprovidedin26SupportingInformation(FigureSI).OnceHisadsorbed,theITphasestructurallytransformsto29theITphase(FigureS2).Thisstructurec
10、hangehelpsadsorptionofHontheITphase,but30123456731anotherimportantfactoristheITphasesmetallicityandpartiallyfilledMo4dstates.42From32 34Figure1,onecanseethatthefreeenergyclosetozerooccursaround12.5%25%Hcoverage353637 (theAGhvalueisbetween-0.28eVand0.13eV).Therefore,itismostlikelythatthehydrogen3838
11、evolutionreactionismainlydrivenbythehydrogenadsorptionat12.5%25%coverage.39 41Particularly,theappropriateHadsorptionenergysuggeststhatthebasalplaneofITM0S2is4243 47.48.50catalyticallyactive,ingoodagreementwithothertheoreticalresults.TheadsorbedH4546 preferstobindtothesurfaceSatoms,regardlessofthecov
12、erage.Ourpreviousworkshowedthat4847 themetastableITM0S2canbestabilizedbyhydrogenationandafteracrossovercoverageof4950 4225%,theITphasebecomesmorestablethanthe2Hphase.Therefore,consideringAGhandtherelativestabilitytogether,onecanseethat25%coverageofhydrogenisoptimal.3.2Thewater-solidinterface.Nowthat
13、wehavefoundouttheoptimalcoverageofHonIT-M0S2,nextweexamineitsHERactivity.Tosimulatethewater-solidinterfaceunderan8 electrochemicalpotential,hereweadoptedanapproachpreviouslyusedbyNorskovetal.in95253545556575859601062elucidatingthereactionmechanismofHERonPt(111)electrode.Theinterfaceregion(orthe11121
14、314Helmholtzlayer)isoftenapproximatedbyabout3Athickelectricaldoublelayer,whichcanbe5representedbyonewaterlayer.Eachprotonconcentrationinthewaterlayercorrespondstoa1617certainelectrodepotentialversusthenormalhydrogenelectrode(NHE),wheretheelectrode192220potentialisdeducedfromthecalculatedworkfunction
15、.Byvaryingthenumberofhydrogen21atomsadded,theelectrostaticpotentialofthewater-solidinterfacecanbevaried.232425Inoursystem,thewater-solidinterfaceinanacidsolutionwasmodeledwithonelayerof27proton-containingwatermoleculesonthesurfaceofH-adsorbedITMoSzmonolayer.We2931consideredintermediate-sized6x43(Fig
16、urea)and9x43(Figure2b低teralcellsofIT-3234353637383933M0S2monolayerwith25%Hcoverage.Todetermineastableconcentrationofprotonsinthesurfacewaterlayer,weperformed10psofDFTmoleculardynamicssimulationatdifferentnumbersofprotonsinthewaterlayerandfoundthattheIT-M0S2monolayerhavingtwoprotons4(orexcesshydrogenatom
