Co_%283%29O_%284%29_石墨炔异质界面用于高效硝酸根制氨.pdf

Cite this:NewCarbonMaterials,2024,39(1):142-151DOI:10.1016/S1872-5805(24)60834-6A Co3O4/graphdiyne heterointerface for efficient ammoniaproduction from nitratesCHENZhao-yang,ZHAOShu-ya,LUANXiao-yu,ZHENGZhi-qiang,YANJia-yu,XUEYu-rui*（Shandong Provincial Key Laboratory for Science of Material Creation and Energy Conversion,Science Center for Material Creation and EnergyConversion,School of Chemistry and Chemical Engineering,Shandong University,Jinan 250100,China）Abstract：Thenitratereductionreaction(NtRR)hasbeendemonstratedtobeapromisingwayforobtainingammonia(NH3)byconverting NO3 to NH3.Here we report the controlled synthesis of cobalt tetroxide/graphdiyne heterostructured nanowires(Co3O4/GDYNWs)byasimpletwo-stepprocessincludingthesynthesisofCo3O4NWsandthefollowinggrowthofGDYusinghex-aethynylbenzeneastheprecursorat110Cfor10h.Detailedscanningelectronmicroscopy,highresolutiontransmissionelectronmicroscopy,X-rayphotoelectronspectroscopy,andRamancharacterizationconfirmedthesynthesisofaCo3O4/GDYheterointerfacewiththeformationofsp-CCobondsattheinterfaceandincompletechargetransferbetweenGDYandCo,whichprovideacon-tinuoussupplyofelectronsforthecatalyticreactionandensurearapidNtRR.Becauseoftheseadvantages,Co3O4/GDYNWshadanexcellentNtRRperformancewithahighNH3yieldrate(YNH3)of0.78mmolh1cm2andaFaradayefficiency(FE)of92.45%at1.05V(vs.RHE).Thisworkprovidesageneralapproachforsynthesizingheterostructuresthatcandrivehigh-performanceammo-niaproductionfromwastewaterunderambientconditions.Key words:Graphdiyne；Heterostructures；Electrocatalysis；Nitratereductionreaction；Ammoniaproduction1IntroductionAmmonia(NH3)is an important feedstock formodernindustryandanidealenergycarrier.Unfortu-nately,industrial-scale NH3 production is mainlybasedonthetraditionalenergy-andemissions-intens-iveHaber-Boschprocessfromnitrogen(NNdisso-ciation energy 941 kJ mol1)and hydrogen underharsh conditions such as high temperatures(673773K)andhighpressures(150300atm)13.Inviewofthis,theelectrochemicalconversionofnitrate(dis-sociationenergy:204kJmol1)intoNH3atroomtem-peraturesandambientpressureshasbeenregardedasthemostpromisingrouteforammoniaproduction47.Forthecomplexeight-electronprocessfromNO3toNH3inNtRR,itisparticularlynecessarytooptimizetheadsorptionanddesorptionbehaviorofbothreact-antsandproductssimultaneously.Thecomplexreac-tionprocessesofvariousreactionintermediates(NO2,NO,NOH,N2,NH2OH,NH2NH2)at the interfaceshouldalsobeconsideredtoimprovetheselectivityofthecatalysts.Tilldate,awidevarietyofcatalystshavebeen reported for efficient NH3 production throughelectrocatalyticnitratereductionreaction(NtRR)813,buttheNH3yieldrates(YNH3)andFaradayefficien-cies(FE)arestillbelowindustrystandardsduetothecomplex eight-electron process from NO3 to NH3conversion.It is therefore of great significance todesignandsynthesizenewcatalystswithhighYNH3,selectivity,andstabilityforobtainingNH3fromNtRR.Amongreportedcatalysts,heterostructuredcata-lystshaveshownmanyintrinsicadvantagestocata-lysiswithimprovedintrinsicactivityandstability1415.Theconstructionofaheterointerfaceisanimportantroutetosynergisticallycombinethead-vantagesofferedbymultiplematerialsandadjustthecatalysts properties such as electrical conductivity,hydrophilicity,interfacial electron modulation,andadsorptionenergyofintermediates,etc1623.Carbon-based materials have become one of the most usedheterojunctionmaterialsduetotheirabundantnaturalReceived date：2023-09-21；Revised date：2023-12-19Corresponding author：XUEYu-rui,Professor.E-mail:Author introduction：CHENZhao-yang,MasterStudent.E-mail:Supplementarydataassociatedwiththisarticlecanbefoundintheonlineversion.Homepage:http:/ specific sp-/sp2-hybridized all-carbon two-dimen-sionalnetworkswithuniquepropertiessuchasanat-uralporestructure,alargespecificsurfacearea,therichalkynebonds,highintrinsicactivityandexcel-lentstability3058.Inaddition,thecontrollablegrowthofGDYonvariousmaterialsurfacesundermildcon-ditions offers the advantage for growing high-per-formanceactivestructures.In this work,we successfully synthesizedCo3O4/GDY heterostructured nanowires by in-situgrowthofGDYonthesurfaceofCo3O4(Fig.1).Thenewly-formed heterointerface between Co3O4 andGDY has improved electric conductivity,increasedactive sites,the specific incomplete charge-transferproperty.These unique advantages of Co3O4/GDYsignificantlypromotetheefficientconversionofNO3toNH3,givingahighYNH3of0.78mmolh1cm2andFEof92.45%at1.05V(vs.RHE).2Experimental 2.1 MaterialsCobalt(II)nitratehexahydrate(Co(NO3)26H2O),ammonium fluoride(NH4F),urea and tetrabutylam-moniumfluoride(TBAF)were purchased from En-ergyChemical.Unless otherwise specified,the re-agentsutilizedinthisstudywereuseddirectly.Thecarbonclothwasthoroughlycleanedbeforeuse.AllwaterusedwaspurifiedwithaMilliporesystem(typ-ically18.2Mcmresistivity).2.2 Synthesis of Co3O4Co3O4wassynthesizedbyasolvothermalmeth-od.Typically,apieceofcarboncloth(CC)(3cm3cm)wasaddedtoaTeflon-linedstainless-steelauto-clave containing 30 mL aqueous solution ofCo(NO3)26H2O(0.36 g),NH4F(0.09 g)and urea(0.375g)andkeptat120Cfor6h.Theprecursorsamplewasobtainedandwashedthoroughlybyde-ionizedwateranddriedat80Cinavacuumoven.Theproductswereannealedat400Cfor2htoob-tainCo3O4samples.2.3 Synthesis of Co3O4/GDYThefreshly-preparedCo3O4wasaddedtotheTe-flon-linedstainless-steelautoclavecontaining30mLhexaethynylbenzenepyridinesolution(0.11mgmL1)andkeptat110Cfor10h.Afterthecompletionofthe reaction,the obtained Co3O4/GDY was cleanedandusedforelectrochemicalmeasurements.Co3O4/GDY heterojunctionCo2+NO3NH3H2ONH4FUreaHEBCarbon clothCo3O4Co3O4/GDYInterfaceFig.1ThesyntheticroutesoftheCo3O4/GDY第1期CHENZhao-yangetal:ACo3O4/graphdiyneheterointerfaceforefficientammoniaproduction143 2.4 CharacterizationsScanning electron microscopy(SEM)imageswere recorded using FEI Apreo SEM.High-resolu-tion(HRTEM)images were taken on Talos F200XTEM.X-rayphotoelectronspectroscopy(XPS,Nexsa)withAlKradiationwasemployedtodeterminethechemical composition and element states.RamanspectrawerecollectedbyaHORIBARamanspectro-meterat473nmlaserexcitationwavelength.Insituattenuatedtotal reflection Fourier transformed in-fraredspectroscopy(ATR-FTIR)wasmeasuredusingINVENIOS(BRUKER).The1HNMRsignalwasac-quired using a Bruker 400 MHz system.(NMR,AVANCEIIIHD400MHz).X-raydiffraction(XRD)wasacquiredusingXPert3Powder(MalvernPana-lytical).2.5 Electrochemical testsElectrochemical tests were performed on CHI760D(there-electrode system;Shanghai CH.Instru-ments,China)in0.5molL1K2SO4+0.1molL1KNO3 using H-type cell separated by Nafion 117membrane.Linear sweep voltammetry(LSV)meas-urementswerecarriedoutatascanrateof2.0mVs1.ChronoamperometrytestswereconductedinAr-satur-ated0.5molL1K2SO4+0.1molL1KNO3aqueoussolution(30mL)undertheAratmosphere.Thechro-noamperometrytestswereusedtomeasuretheper-formanceofthecatalystelectrodeat1.5,1.6,1.7,1.8and1.9V(vs.SCE).Electrochemicalimped-ancespectra(EIS)wererecordedinafrequencyrangespanningfrom100kHzto0.01Hz.3ResultsanddiscussionFig.1showsthesynthesisrouteofCo3O4/GDY.Inbrief,theas-synthesizedCo3O4wasdirectlyusedassupporting material for growing GDY to obtainCo3O4/GDYsamples.Inthisprocess,Co3O4actsasboth the growing template and the catalyst for thecouplingreactionofhexaethynylbenzene(HEB).HEBmolecules gradually polymerize under the catalyticaction of Co species on the surface of Co3O4,ulti-matelyobtainingaGDYlayerattheinterface.Thesize,morphology,andstructureofthesampleswerecharacterized by SEM and HRTEM measurements.AfterhydrophilictreatmentandcleaningofrawCC,thesmoothCCwithoutanyimpuritieswasobtained(Fig.S1a-b).Afterthehydrothermalreaction,Copre-cursorsweresuccessfullyloadedontothesurfaceoftheCC(Fig.S2a-b).Next,itwasannealedat400CtoobtaintheCo3O4withananowires-likestructure.AsshowninFig.2a-c,Co3O4nanowireswithho-mogeneous size and distribution were uniformlygrownon carbon fibers.The exposed Co sites be-comeidealsitesforGDYgrowthandsubsequentcata-lyticreactions.Afterthein-situgrowthofGDY,theCo3O4/GDYexhibitsaroughersurfaceandmaintainsoriginalnanowiresmorphologyascomparedtothoseof pristine Co3O4(Fig.2d-f).The 3D structure androughsurfacecanenlargethespecificareaforcatalys-is.Fig.2gshowstheevendispersionofC,CoandOinCo3O4/GDY.ComparedtoCC,thehydrophilicityoftheCo3O4/GDYissignificantlyenhanced(Fig.2h),whichfacilitates the transportation of reaction sub-strates,intermediates,and products at the interface.TheopticalimagesareshowninFig.2i.Theas-pre-paredCo3O4/GDYisquiteflexible,whichmakesitapotentialcandidateforflexibledevicesthatcanbeap-pliedinmicroammoniaproduction.Thesecharacter-isticsmakeGDYanidealcatalyticmaterial.HRTEMimages(Fig.3a-c)revealthecrystallinenature of Co3O4,featuring(200),(211),(112)and(103)planes.The lattice spacings of Co3O4/GDYchanges slightly(Fig.3d)due to the interactionbetweenCo3O4andGDY.TheuniformdistributionofCo3O4speciescanbeobservedinFig.3e.Aclearin-terfacebetweenCo3O4andGDYismarkedinFig.3f,indicatingtheheterointerfacebetweendifferentcrys-tallinephases,consistentwiththeaboveresults.Tofurther explore the characteristics of GDY inCo3O4/GDY,theregionswhereonlyGDYexistsareselected(Fig.3g).ThelatticespacingsofGDYwerefoundtobe0.370and0.395nm(Fig.3h.)ThestackedGDYlayersaremarkedinFig.3i.TheseobservationsprovethatCo3O4/GDYheterointerfaceswereformedsuccessfully.This was further confirmed by XRDmeasurements(Fig.S4).144新型炭材料（中英文）第39卷CCbeforeCOCoCCafterGDYbeforeGDYafter10 nm10 nm1 nm1 nm5 nm5 nm(d)(a)(b)(c)(e)(f)(g)(h)(i)Fig.2Morphologicalcharacterizationsofsamples.(a)Low-and(b,c)high-magnificationSEMimagesoftheCo3O4.(d)Low-and(e,f)high-magnificationSEMimagesoftheas-preparedCo3O4/GDY.(g)EDSmappingofC,OandCoinCo3O4/GDYnanowires.(h)ContactanglemeasurementsofCo3O4/GDY.(i)OpticalphotosofCo3O4/GDY10 nm(2 1 1)10 nm(2 0 0)10 nm(1 0 3)(2 0 0)(1 1 2)0.287 nm0.249 nm0.286 nm0.290 nm0.244 nm(2 0 0)Stacked GDY5 nm2 nmGDY10 nm0.245 nm0.282 nm0.286 nm-Co3O4Interface0.285 nm0.370 nm0.395 nm10 nm10 nm(a)(b)(c)(d)(e)(f)(g)(h)(i)10 nmFig.3(a-c)HRTEMimagesoftheCo3O4.(d-f)HRTEMimagesoftheCo3O4/GDY.(e)ThehighdistributionofCo3O4inCo3O4/GDY.(f)BoundarybetweenCo3O4andGDY.(g)Low-and(h,i)high-magnificationHRTEMimagesofGDYonthesurfaceofCo3O4/GDY第1期CHENZhao-yangetal:ACo3O4/graphdiyneheterointerfaceforefficientammoniaproduction145XPSsurveyspectra(Fig.S3)showthecoexist-enceofCo,CandOinbothCo3O4andCo3O4/GDY.The Raman peaks corresponding the alkyne bonds(1877 and 2096 cm1)were observed in Co3O4/GDY5960.Compared with GDY(Fig.S5),the redshiftofCo3O4/GDYisascribedtothetensilestrainsofthealkynebondinCo3O4/GDY.Theseresultsprovethe existence of the interaction between Co3O4 andGDY,which is consistent with the HRTEM.Com-paredwiththeinitialCo3O4,threenewpeaksofsp-C(285.02eV),CoC(283.16eV),and-*interac-tion(290.68 eV)appear in Co3O4/GDY(Fig.4b).Fig.4cshowstheexistenceofamixedvalencestateof Co2+with Co3+in Co3O4/GDY.Compared withpureCo3O4,theCo2+bindingenergyofCo3O4/GDYslightlydecreases.ThismightbeduetotheelectrontransferredfromGDYspecies.Fig.4dshowsthatthesurface-OHratioinCo3O4/GDYishigherthanCo3O4,whichisbeneficialtoelectrochemicalmasstransfer(Fig.S6).The conversion of valence between Co3+andCo2+occursintheas-formedinterface(Fig.4e).Toinvestigatetheintrinsicmechanismofhighcatalyt-(d)(e)(f)(i)(h)(g)(c)(b)(a)Co3O4Co3O4/GDYCo3O4/GDYCo3O4/GDY:2.35 mF cm2Co3O4:1.95 mF cm2Incomplete charge transferon heterjunction interfaceCo3O4Co3O4/GDYCo3O4Co3O4/GDYCo3O4/GDY after NtRRCo3O4Co3O4/GDYCo 2p1/2Co 2p1/2Co 2p3/2Co 2pCo 2p3/2Co 2pCo3O4sp2-CC-OC=Osp-CCo-C-*Co3+Co2+Sat.Co2+Co3+Sat.Intensity/(a.u.)Intensity/(a.u.)Intensity/(a.u.)Intensity/(a.u.)Intensity/(a.u.)Raman shift/cm1OO 1sC 1sOOBinding energy/eVBinding energy/eVBinding energy/eVNH3NO3NH3Co3+Co2+Co3O4/GDYBinding energy/eVZ/Z/Scan rate/(mV s1)j/(mA cm2)Fig.4(a)RamanspectraofCo3O4andCo3O4/GDY.(b)C1sXPSspectraofCo3O4andCo3O4/GDY.(c)Co2pXPSspectraofCo3O4andCo3O4/GDY.(d)O1sXPSspectraofCo3O4andCo3O4/GDY.OrepresentstheCo-Obond;OisassignedastheOHonthesurface;Oisconsideredtooriginatefromenvir-onmentalcontamination.(e)SchematicillustrationoftheelectrontransferattheGDY-Co3O4interfacesofCo3O4/GDY.(f)Thecurrentdensitydifferences(j=jajc)areplottedagainstscanrates.(g)NyquistplotsofCo3O4andCo3O4/GDY.(h)Co2pXPSspectraofCo3O4/GDYafterNtRR.(i)SchematicdiagramofchargechangesinCo3O4/GDYduringtheNtRRprocess146新型炭材料（中英文）第39卷icactivityinCo3O4/GDY,CVandEISwereapplied.TheresultsshowthatCo3O4/GDYpossessesalargerelectrochemicalactivesurfaceareaandlowerresist-ance(Fig.4f-g,Fig.S7).TheC1s,O1sandCo2pXPS analysis of Co3O4/GDY obtained after NtRR(Fig.S8,Fig.4h)reveal that sp-C,CoC,and-*dontdisappear,affirmingthestructuralstabilityof the Co3O4/GDY.The Co 2p XPS spectra ofCo3O4/GDY(Fig.4c,4h)show a substantial trans-itionfromCo2+toCo3+duringtheNtRRprocess,in-dicatingthatthevalencestateofCospecieschangesduring the catalytic process(Fig.4i).The abundantelectronsofthealkynebondintheGDYundergoin-completechargetransferbehaviorwithCo3O4,stabil-izingelectrontransportattheinterface.Inaddition,GDY can serve as a continuous electron storagespace,whichguaranteessufficientelectronsupplyattheinterface,thussupportingthecomplexeight-elec-trontransferprocessfromNO3toNH3.Thesecharac-teristicsenableCo3O4/GDYtobecometheidealma-terialofNtRR.Next,theNtRRperformanceofCo3O4/GDYwasmeasured at 300 K and 101 kPa.The Ar-saturated0.5molL1K2SO4+0.1molL1KNO3wasusedastheelectrolyte.Allpotentialswereconvertedtoare-versible hydrogen electrode(RHE).The schematicrepresentation of the NO3-to-NH3 conversion isshowninFig.5a.Fig.5bshowstheLSVcurvesofCo3O4andCo3O4/GDYinelectrolyteswithorwithoutKNO3,respectively.As the applied potential in-creases,bothCo3O4andCo3O4/GDYexhibitastrongcurrentresponsetoNO3reduction,indicatingtheoc-currenceofNtRRinthepresenceofNO3.ComparedwithCo3O4,Co3O4/GDYexhibitsastrongerresponsetrend,which indicates that the combination of theGDYandCo3O4cansignificantlyimprovecatalyticactivitydue to the formation of highly active het-erointerfacesbetweenGDYandCo3O4withincom-plete charge transfer and enhanced conductivity.Fig.5c shows the chronoamperometric curves ofCo3O4/GDYatdifferentpotentials.Asexpected,thecurrent density of Co3O4/GDYis significantly in-creasedwithamorenegativepotential,followedbyanincreasingcompetitionforhydrogenevolutionre-action(HER).Ultraviolet-visible(UV-Vis)spectro-photometrywasemployedtodeterminetheconcentra-tionoftheproducedNH3fortheelectrolyteafterelec-trolysisbytheindophenolbluemethod.Co3O4/GDYexhibitssuperiorcatalyticperformancewithFaradayefficiency(FE)reaching over 80%at full potential(Fig.5e).TheFEandammoniaproductionrate(YNH3)ofCo3O4/GDYreachthehighestvaluesof92.45%and0.78mmolh1cm2,respectively,whichgreatlyex-ceedsbareCo3O4beforethein-situgrowthofGDY(Fig.5d).Toinvestigatethestabilityofthecatalyst,Co3O4/GDYwastestedfor8catalyticcycles(Fig.5f,Fig.S10).The results show that the Co3O4/GDYmaintainedhighYNH3andFEduringthetestingperiod,without significant performance degradation.TheseresultsdemonstratethestabilizingeffectofGDYontheCo3O4interface.WithouttheadditionofNO3,noammoniawasdetectedafterelectrolysisforthesametime(Fig.5g,Fig.S14),provingthatallthegen