Enhancing the photocatalytic activity and photostability of zinc oxide nanorod arrays via graphitic carbon mediation

Article abstract of DOI:10.1016/S1872-2067(18)63010-4

Low optical absorption and photocorrosion are two crucial issues limiting the practical applications of zinc oxide (ZnO)-based photocatalysts. In this paper, we report the fabrication of graphitic-carbon-mediated ZnO nanorod arrays (NRAs) with enhanced ph

Full text of DOI:10.1016/S1872-2067(18)63010-4

ChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ973–981
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ꢀ ꢀ ꢀ
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a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
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j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
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Article
Enhancingꢀtheꢀphotocatalyticꢀactivityꢀandꢀphotostabilityꢀofꢀzincꢀ ꢀ
oxideꢀnanorodꢀarraysꢀviaꢀgraphiticꢀcarbonꢀmediationꢀ
XueweiꢀZhangꢀ ,ꢀXueliangꢀZhangꢀ ,ꢀXinꢀWangꢀ ,ꢀLequanꢀLiuꢀ ,ꢀJinhuaꢀYeꢀa,b,c,ꢀDefaꢀWangꢀa,b,*
a
a
a
a,b
ꢀ
aꢀTJU‐NIMSꢀInternationalꢀCollaborationꢀLaboratory,ꢀKeyꢀLabꢀofꢀAdvancedꢀCeramicsꢀandꢀMachiningꢀTechnologyꢀofꢀMinistryꢀofꢀEducation,ꢀTianjinꢀKeyꢀLabꢀ
ofꢀCompositeꢀandꢀFunctionalꢀMaterials,ꢀSchoolꢀofꢀMaterialsꢀScienceꢀandꢀEngineering,ꢀTianjinꢀUniversity,ꢀTianjinꢀ300072,ꢀChinaꢀ
bꢀCollaborativeꢀInnovationꢀCenterꢀofꢀChemicalꢀScienceꢀandꢀEngineeringꢀ(Tianjin),ꢀTianjinꢀ300072,ꢀChinaꢀ
cꢀInternationalꢀCenterꢀofꢀMaterialsꢀNanoarchitectonicsꢀ(WPI‐MANA),ꢀNationalꢀInstituteꢀforꢀMaterialsꢀScienceꢀ(NIMS),ꢀIbarakiꢀ305‐0044,ꢀJapanꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
Lowꢀopticalꢀabsorptionꢀandꢀphotocorrosionꢀareꢀtwoꢀcrucialꢀissuesꢀlimitingꢀtheꢀpracticalꢀapplicationsꢀ
ofꢀ zincꢀ oxideꢀ (ZnO)‐basedꢀ photocatalysts.ꢀ Inꢀ thisꢀ paper,ꢀ weꢀ reportꢀ theꢀ fabricationꢀ ofꢀ graphit‐
ic‐carbon‐mediatedꢀZnOꢀnanorodꢀarraysꢀ(NRAs)ꢀwithꢀenhancedꢀphotocatalyticꢀactivityꢀandꢀphoto‐
Receivedꢀ18ꢀNovemberꢀ2017ꢀ
Acceptedꢀ28ꢀDecemberꢀ2017ꢀ
Publishedꢀ5ꢀMayꢀ2018ꢀ
stabilityꢀforꢀCO ꢀreductionꢀunderꢀvisibleꢀlightꢀirradiation.ꢀZnOꢀNRA/C‐xꢀ(xꢀ=ꢀ005,ꢀ01,ꢀ02,ꢀandꢀ03)ꢀ
2
nanohybridsꢀareꢀpreparedꢀbyꢀcalciningꢀpre‐synthesizedꢀZnOꢀNRAsꢀwithꢀdifferentꢀamountsꢀofꢀglu‐
coseꢀ(0.05,ꢀ0.1,ꢀ0.2,ꢀandꢀ0.3ꢀg)ꢀasꢀaꢀcarbonꢀsourceꢀviaꢀaꢀhydrothermalꢀmethod.ꢀX‐rayꢀphotoelectronꢀ
spectroscopyꢀrevealsꢀthatꢀtheꢀobtainedꢀZnOꢀNRA/C‐xꢀnanohybridsꢀareꢀimpartedꢀwithꢀtheꢀeffectsꢀofꢀ
bothꢀcarbonꢀdopingꢀandꢀcarbonꢀcoating,ꢀasꢀevidencedꢀbyꢀtheꢀdetectedꢀCOZnꢀbondꢀandꢀtheꢀCC,ꢀ
COꢀandꢀC=Oꢀbonds,ꢀrespectively.ꢀWhileꢀtheꢀbasicꢀstructureꢀofꢀZnOꢀremainsꢀunchanged,ꢀtheꢀUV‐Visꢀ
absorptionꢀ spectraꢀ showꢀ increasedꢀ absorbanceꢀ owingꢀ toꢀ theꢀ carbonꢀ dopingꢀ effectꢀ inꢀ theꢀ ZnOꢀ
NRA/C‐xꢀ nanohybrids.ꢀ Theꢀ photoluminescenceꢀ(PL)ꢀintensitiesꢀofꢀZnOꢀNRA/C‐xꢀnanohybridsꢀareꢀ
lowerꢀthanꢀthatꢀofꢀbareꢀZnOꢀNRA,ꢀindicatingꢀthatꢀtheꢀgraphiticꢀcarbonꢀlayerꢀcoatedꢀonꢀtheꢀsurfaceꢀofꢀ
theꢀZnOꢀNRAꢀsignificantlyꢀenhancesꢀtheꢀchargeꢀcarrierꢀseparationꢀandꢀtransport,ꢀwhichꢀinꢀturnꢀen‐
hancesꢀtheꢀphotoelectrochemicalꢀpropertyꢀandꢀphotocatalyticꢀactivityꢀofꢀtheꢀZnOꢀNRA/C‐xꢀnanohy‐
Keywords:ꢀ
Photocatalysisꢀ
ZnOꢀnanorodꢀarrayꢀ
Graphiticꢀcarbonꢀ
Chargeꢀtransferꢀ
Photostabilityꢀ
2
CO ꢀreduction
bridsꢀ forꢀ CO
2
ꢀ reduction.ꢀ Moreꢀ importantly,ꢀ aꢀ long‐termꢀ reactionꢀ ofꢀ photocatalyticꢀ CO ꢀ reductionꢀ
2
demonstratesꢀ thatꢀ theꢀ photostabilityꢀ ofꢀ ZnOꢀ NRA/C‐xꢀ nanohybridsꢀ isꢀ significantlyꢀ increasedꢀ inꢀ
comparisonꢀwithꢀtheꢀbareꢀZnOꢀNRA.ꢀ
©ꢀ2018,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
1
.ꢀ ꢀ Introductionꢀ
[6–16],ꢀ amongꢀ whichꢀ zincꢀ oxideꢀ (ZnO)ꢀ hasꢀ beenꢀ intensivelyꢀ
studiedꢀbecauseꢀofꢀitsꢀattractiveꢀphotophysicalꢀpropertiesꢀandꢀ
nontoxicityꢀ[17–20].ꢀHowever,ꢀtheꢀpracticalꢀapplicationꢀofꢀZnOꢀ
asꢀaꢀphotocatalystꢀhasꢀhardlyꢀbeenꢀrealized.ꢀThisꢀhasꢀbeenꢀbe‐
causeꢀofꢀitsꢀlowꢀphotostabilityꢀthatꢀisꢀcausedꢀbyꢀphotocorrosionꢀ
[21–24],ꢀinꢀwhichꢀtheꢀzincꢀionꢀisꢀproneꢀtoꢀoxidationꢀbyꢀphoto‐
generatedꢀholesꢀuponꢀlightꢀirradiation.ꢀZnOꢀisꢀaꢀwideꢀbandꢀgapꢀ
Photocatalysisꢀ usingꢀ semiconductorsꢀ andꢀ solarꢀ energyꢀ forꢀ
waterꢀsplittingꢀtoꢀgenerateꢀhydrogenꢀandꢀrecyclingꢀCO ꢀbackꢀtoꢀ
2
hydrocarbonꢀfuelsꢀhasꢀattractedꢀwideꢀattention,ꢀinꢀviewꢀofꢀtheꢀ
globalꢀ energyꢀ crisisꢀ andꢀ environmentꢀ pollutionꢀ issuesꢀ [18].ꢀ
Overꢀtheꢀpastꢀfourꢀdecades,ꢀtremendousꢀeffortsꢀhaveꢀbeenꢀde‐
votedꢀ toꢀ developingꢀ variousꢀ semiconductorꢀ photocatalystsꢀ
(E
g
ꢀꢀ3.2ꢀeV)ꢀsemiconductor,ꢀsoꢀitꢀcanꢀonlyꢀabsorbꢀultravioletꢀ
*ꢀCorrespondingꢀauthor.ꢀTel/Fax:ꢀ+86‐22‐27405065;ꢀE‐mail:ꢀdefawang@tju.edu.cnꢀ
ThisꢀworkꢀwasꢀsupportedꢀbyꢀtheꢀNationalꢀBasicꢀResearchꢀProgramꢀofꢀChinaꢀ(973ꢀProgram,ꢀ2014CB239300),ꢀtheꢀNationalꢀNaturalꢀScienceꢀFoundationꢀ
ofꢀChinaꢀ(51572191,ꢀ21633004),ꢀandꢀtheꢀNaturalꢀScienceꢀFoundationꢀofꢀTianjinꢀCityꢀ(13JCYBJC16600).ꢀ ꢀ
DOI:ꢀ10.1016/S1872‐2067(18)63010‐4ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ39,ꢀNo.ꢀ5,ꢀMayꢀ2018ꢀ ꢀ ꢀ

974ꢀ
XueweiꢀZhangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ973–981ꢀ
(
UV)ꢀwavelengths.ꢀUVꢀwavelengthsꢀconstituteꢀonlyꢀ4%ꢀofꢀtheꢀ
comparedꢀwithꢀtheꢀZnOꢀNRA.ꢀTheꢀgraphiticꢀcarbonꢀlayerꢀcoatedꢀ
onꢀ theꢀ surfaceꢀ ofꢀ theꢀ ZnOꢀ NRAꢀ significantlyꢀ enhancesꢀ chargeꢀ
carrierꢀseparationꢀandꢀtransportꢀandꢀthusꢀenhancesꢀtheꢀphoto‐
catalyticꢀactivityꢀofꢀtheꢀZnOꢀNRA/C‐xꢀnanohybrids.ꢀThisꢀstudyꢀ
providesꢀ aꢀ methodꢀ involvingꢀ graphiticꢀ carbonꢀ mediationꢀ forꢀ
fabricatingꢀaꢀhighlyꢀstableꢀandꢀactiveꢀZnO‐basedꢀphotocatalystꢀ
solarꢀ spectrum,ꢀ soꢀ longerꢀ visibleꢀ wavelengthsꢀ areꢀ effectivelyꢀ
wastedꢀ[25–27].ꢀPreviousꢀstudiesꢀhaveꢀshownꢀthatꢀdopingꢀwithꢀ
C,ꢀN,ꢀorꢀSꢀcouldꢀextendꢀtheꢀopticalꢀabsorptionꢀrangeꢀofꢀZnOꢀintoꢀ
theꢀvisibleꢀregion.ꢀLinꢀetꢀal.ꢀ[28]ꢀpreparedꢀhierarchicallyꢀporousꢀ
nanoarchitecturesꢀofꢀC‐dopedꢀZnOꢀbyꢀaꢀfacileꢀandꢀinexpensiveꢀ
wet‐chemicalꢀmethod.ꢀChoꢀetꢀal.ꢀ[29]ꢀusedꢀvitaminꢀCꢀasꢀaꢀcarbonꢀ
sourceꢀtoꢀsynthesizeꢀC‐dopedꢀZnOꢀasꢀaꢀvisibleꢀlightꢀphotocata‐
lyst.ꢀ
forꢀCO
ꢀreduction.ꢀ
2
2.ꢀ ꢀ Experimentalꢀ
Efficientꢀchargeꢀseparationꢀandꢀtransferꢀareꢀessentialꢀforꢀef‐
ficientꢀphotocatalyticꢀactivityꢀ[30,31].ꢀHowꢀtoꢀsuppressꢀtheꢀre‐
combinationꢀ ofꢀ photoinducedꢀ chargeꢀ carriersꢀ (electron/holeꢀ
pairs)ꢀ hasꢀ longꢀ beenꢀ aꢀ challengeꢀ inꢀ photocatalysisꢀ [32,33].ꢀ Aꢀ
photocatalyticꢀreactionꢀisꢀaꢀsurface‐basedꢀprocessꢀinvolvingꢀtheꢀ
separationꢀ andꢀ transportꢀ ofꢀ photoinducedꢀ chargeꢀ carriers,ꢀ asꢀ
theꢀ subsequentꢀ redoxꢀ reactionsꢀ mainlyꢀ occurꢀ onꢀ theꢀ catalystꢀ
surface.ꢀ One‐dimensionalꢀ (1‐D)ꢀ semiconductorsꢀ haveꢀ largeꢀ
surface‐to‐volumeꢀ ratiosꢀ andꢀ goodꢀ chargeꢀ carrierꢀ transportꢀ
ratesꢀ whichꢀ benefitꢀ fromꢀ theꢀ ballisticꢀ effect.ꢀ Thus,ꢀ 1‐Dꢀ semi‐
conductorsꢀ areꢀ expectedꢀ toꢀ exhibitꢀ superiorꢀ photocatalyticꢀ
activityꢀ comparedꢀ withꢀ conventionalꢀ powderꢀ photocatalystsꢀ
2.1.ꢀ ꢀ Sampleꢀpreparationꢀ
TheꢀZnOꢀnanorodꢀarrayꢀwasꢀdirectlyꢀgrownꢀonꢀzincꢀfoilꢀ(2.0ꢀ
cmꢀꢀ3.0ꢀcm)ꢀviaꢀaꢀhydrothermalꢀmethodꢀatꢀ180ꢀ°Cꢀforꢀ4ꢀh,ꢀinꢀaꢀ
solutionꢀcontainingꢀ25ꢀmLꢀofꢀH
2
O,ꢀ2ꢀgꢀofꢀNaOH,ꢀandꢀ3.6ꢀmLꢀofꢀ
30%ꢀ H .ꢀ Theꢀ surfaceꢀ ofꢀ theꢀ zincꢀ foilꢀ wasꢀ pretreatedꢀ usingꢀ
2 2
O
hydrochloricꢀacidꢀforꢀ20ꢀs.ꢀAfterꢀrinsingꢀwithꢀdeionizedꢀwaterꢀ
severalꢀ times,ꢀ theꢀ synthesizedꢀ ZnOꢀ NRAꢀ onꢀ theꢀ zincꢀ foilꢀ wasꢀ
driedꢀ atꢀ roomꢀ temperature.ꢀ Aꢀ typicalꢀ procedureꢀ forꢀ coatingꢀ
carbonꢀonꢀ theꢀ ZnOꢀNRAꢀwasꢀasꢀ follows.ꢀDifferentꢀ amountsꢀofꢀ
glucoseꢀ(0.05,ꢀ0.1,ꢀ0.2,ꢀ0.3ꢀg)ꢀwereꢀfirstꢀdissolvedꢀinꢀ30ꢀmLꢀofꢀ
deionizedꢀwater,ꢀintoꢀwhichꢀtheꢀZnOꢀ NRAꢀwasꢀadded;ꢀtheꢀre‐
sultingꢀsolutionꢀwasꢀthenꢀheatedꢀtoꢀ180ꢀ°Cꢀforꢀ4ꢀh,ꢀfollowedꢀbyꢀ
coolingꢀ toꢀ roomꢀ temperature.ꢀ Afterꢀ washingꢀ withꢀ deionizedꢀ
waterꢀseveralꢀtimes,ꢀtheꢀsamplesꢀwereꢀdriedꢀinꢀanꢀovenꢀatꢀ80ꢀ°Cꢀ
forꢀ1ꢀh.ꢀFinally,ꢀtheꢀsamplesꢀwereꢀplacedꢀinꢀaꢀtubeꢀfurnaceꢀandꢀ
calcinedꢀatꢀ800ꢀ°Cꢀwithꢀaꢀheatingꢀrateꢀofꢀ5ꢀ°C/minꢀforꢀ3ꢀhꢀinꢀanꢀ
argonꢀ gasꢀ atmosphere,ꢀ toꢀ obtainꢀ theꢀ resultingꢀ samplesꢀ
ZnO‐NRA/C‐xꢀ (whereꢀ xꢀ =ꢀ 005,ꢀ 01,ꢀ 02,ꢀ andꢀ 03,ꢀ andꢀ denotesꢀ
addedꢀglucoseꢀamountsꢀofꢀ0.05,ꢀ0.1,ꢀ0.2,ꢀandꢀ0.3ꢀg,ꢀrespectively).ꢀ
Forꢀcomparison,ꢀzincꢀfoilꢀcoatedꢀwithꢀgraphiticꢀcarbonꢀ(denotedꢀ
asꢀZn/Cꢀfoil)ꢀwasꢀalsoꢀpreparedꢀfollowingꢀaꢀsimilarꢀprocedureꢀ
asꢀmentionedꢀabove.ꢀ ꢀ
[34,35].ꢀCoatingꢀaꢀthinꢀamorphousꢀcarbonꢀlayerꢀonꢀtheꢀsurfaceꢀ
ofꢀ aꢀ semiconductorꢀ hasꢀ beenꢀ demonstratedꢀ toꢀ effectivelyꢀ im‐
proveꢀ chargeꢀ carrierꢀ separation.ꢀ Inꢀ thisꢀ context,ꢀ manyꢀ recentꢀ
studiesꢀ haveꢀ reportedꢀ theꢀ coatingꢀ ofꢀ 1‐Dꢀ ZnOꢀ withꢀ aꢀ carbonꢀ
layerꢀ toꢀ suppressꢀ chargeꢀ carrierꢀ recombination,ꢀ andꢀ inꢀ turnꢀ
improveꢀ theꢀ photocatalyticꢀ activity.ꢀ Muꢀ etꢀ al.ꢀ [36]ꢀ preparedꢀ
ZnOcarbonꢀ nanofiberꢀ heteroarchitecturesꢀ withꢀ highꢀ photo‐
catalyticꢀ activityꢀ forꢀ degradingꢀ rhodamineꢀ B.ꢀ Hanꢀ etꢀ al.ꢀ [37]ꢀ
reportedꢀ theꢀ enhancedꢀ photocatalyticꢀ activityꢀ andꢀ an‐
ti‐photocorrosionꢀpropertiesꢀofꢀZnOꢀbyꢀcouplingꢀwithꢀversatileꢀ
carbonꢀ species.ꢀ Aꢀ microwave‐assistedꢀ carbonizationꢀ strategyꢀ
wasꢀadoptedꢀbyꢀGuoꢀetꢀal.ꢀ[38]ꢀtoꢀformꢀaꢀuniformꢀcarbonꢀcoat‐
ingꢀonꢀZnOꢀnanorods,ꢀwhichꢀenhancedꢀtheirꢀphotocatalyticꢀac‐
tivity.ꢀYuꢀetꢀal.ꢀ[39]ꢀsynthesizedꢀZnOcarbonꢀquantumꢀdotsꢀbyꢀaꢀ
one‐stepꢀmethod,ꢀandꢀtheꢀresultingꢀmaterialꢀexhibitedꢀexcellentꢀ
photocatalyticꢀ abilityꢀ forꢀ toxicꢀ gasꢀ degradationꢀ underꢀ visibleꢀ
lightꢀirradiation.ꢀAkirꢀetꢀal.ꢀ[40]ꢀsynthesizedꢀcarbon‐ZnOꢀnano‐
compositesꢀ withꢀ enhancedꢀ visibleꢀ lightꢀ photocatalyticꢀ perfor‐
manceꢀ forꢀ degradingꢀ rhodamineꢀ B.ꢀ Othersꢀ haveꢀ synthesizedꢀ
2.2.ꢀ ꢀ Characterizationꢀ ꢀ
Theꢀcrystalꢀstructuresꢀofꢀtheꢀsynthesizedꢀsamplesꢀwereꢀde‐
terminedꢀ usingꢀ aꢀ powderꢀ X‐rayꢀ diffractometerꢀ (XRD;ꢀ Cuꢀ Kꢀ
radiation,ꢀ D8ꢀ Advanced,ꢀ Bruker,ꢀ Germany).ꢀ Microstructuresꢀ
wereꢀobservedꢀusingꢀaꢀfield‐emissionꢀscanningꢀelectronꢀmicro‐
scopeꢀ (FESEM;ꢀ JOELS4800,ꢀ Japan)ꢀ andꢀ aꢀ transmissionꢀ elec‐
tronꢀmicroscopeꢀ(TEM;ꢀFEIꢀTecnaiꢀG2ꢀF20,ꢀUSA),ꢀbothꢀequippedꢀ
withꢀanꢀenergyꢀdispersiveꢀX‐rayꢀspectrometer.ꢀRamanꢀscatter‐
ingꢀ spectraꢀ wereꢀ recordedꢀ usingꢀ aꢀ Ramanꢀ spectroscopeꢀ
(XploRAꢀPLUS,ꢀHORIBAꢀScientific,ꢀNJ,ꢀUSA).ꢀTheꢀopticalꢀproper‐
tiesꢀofꢀtheꢀsamplesꢀwereꢀcharacterizedꢀbyꢀmeasuringꢀtheirꢀul‐
traviolet‐visibleꢀ (UV‐Vis)ꢀ diffuseꢀ reflectanceꢀ spectraꢀ withꢀ aꢀ
spectrophotometerꢀ (UV‐2700,ꢀ Shimazu,ꢀ Japan)ꢀ andꢀ photolu‐
minescenceꢀ(PL)ꢀspectraꢀwithꢀaꢀfluorescenceꢀspectrophotome‐
terꢀ(Fluorolog‐3,ꢀHORIBAꢀScientific,ꢀNJ,ꢀUSA),ꢀrespectively.ꢀTheꢀ
valenceꢀ statesꢀ ofꢀ near‐surfaceꢀ elementsꢀ wereꢀ measuredꢀ byꢀ
X‐rayꢀ photoelectronꢀ spectroscopyꢀ (XPS;ꢀ Escalabꢀ 250,ꢀ Thermoꢀ
Scientific,ꢀMA,ꢀUSA).ꢀXPSꢀspectraꢀwereꢀcalibratedꢀusingꢀtheꢀCꢀ1sꢀ
peakꢀ(284.8ꢀeV)ꢀasꢀtheꢀreference.ꢀ
ZnO‐nanoparticle/graphene‐oxideꢀ orꢀ ZnO‐nanorod/
graphene‐oxideꢀcompositesꢀforꢀtheꢀphotodegradationꢀofꢀmeth‐
yleneꢀblueꢀ[41,42].ꢀHowever,ꢀpreviousꢀstudiesꢀonꢀcarbon‐modi‐
ꢀ
reduced‐
ꢀ
ꢀ
fiedꢀ ZnOꢀ haveꢀ rarelyꢀ focusedꢀ onꢀ comprehensivelyꢀ improvingꢀ
theꢀphotostability,ꢀchargeꢀcarrierꢀseparation,ꢀandꢀphotocatalyticꢀ
2
CO ꢀreductionꢀ[26].ꢀ
Herein,ꢀweꢀreportꢀaꢀmodifiedꢀhydrothermalꢀmethodꢀforꢀfab‐
ricatingꢀ graphitic‐carbon‐mediatedꢀ visible‐light‐responsiveꢀ
ZnOꢀ nanorodꢀ arraysꢀ (NRAs).ꢀ Theꢀ resultingꢀ carbon‐containingꢀ
NRAsꢀexhibitꢀenhancedꢀphotocatalyticꢀactivityꢀandꢀphotostabil‐
ityꢀ forꢀ CO ꢀ reduction,ꢀ comparedꢀ withꢀ theꢀ NRAꢀ containingꢀ noꢀ
2
carbon.ꢀ Byꢀ calciningꢀ pre‐synthesizedꢀ ZnOꢀ NRAsꢀ coatedꢀ withꢀ
differentꢀamountsꢀofꢀglucoseꢀasꢀaꢀcarbonꢀsourceꢀatꢀaꢀsuitableꢀ
hydrothermalꢀ temperature,ꢀ weꢀ obtainꢀ ZnOꢀ NRA/C‐xꢀ nanohy‐
bridsꢀonꢀzincꢀfoil.ꢀTheꢀZnOꢀNRA/C‐xꢀnanohybridsꢀareꢀimpartedꢀ
withꢀtheꢀeffectsꢀofꢀbothꢀcarbonꢀdopingꢀandꢀcarbonꢀcoating,ꢀsoꢀ
theyꢀ exhibitꢀ increasedꢀ absorptionꢀ abilityꢀ andꢀ photostabilityꢀ
2.3.ꢀ ꢀ Evaluationꢀofꢀphotoelectrochemicalꢀ(PEC)ꢀandꢀ ꢀ
photocatalyticꢀactivitiesꢀ

ꢀ
XueweiꢀZhangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ973–981ꢀ
975ꢀ
TheꢀPECꢀperformancesꢀofꢀtheꢀsamplesꢀwereꢀmeasuredꢀusingꢀ
anꢀ electrochemicalꢀ workstationꢀ (CHI660E,ꢀ Shanghai,ꢀ China)ꢀ
withꢀaꢀconventionalꢀthree‐electrodeꢀsystem,ꢀwithꢀNa SO ꢀsolu‐
tionꢀ(0.1ꢀmol/L)ꢀ asꢀtheꢀelectrolyteꢀunderꢀvisibleꢀlightꢀirradia‐
tion.ꢀTheꢀZnOꢀNRA/C‐xꢀfoilꢀsampleꢀwithꢀanꢀirradiationꢀareaꢀofꢀ
h,ꢀinꢀaꢀsolutionꢀcontainingꢀ25ꢀmLꢀofꢀH
2
O,ꢀ2ꢀgꢀofꢀNaOHꢀandꢀ3.6ꢀ
mLꢀofꢀ30%ꢀH O ꢀ[43].ꢀThen,ꢀgraphiticꢀcarbon‐hybridizedꢀZnOꢀ
2
2
2
4
NRAꢀnanocompositesꢀwereꢀpreparedꢀbyꢀaꢀhydrothermalꢀmeth‐
odꢀandꢀsubsequentꢀcarbonizationꢀofꢀtheꢀpre‐adsorbedꢀglucose.ꢀ
Fig.ꢀ 1(a)ꢀ showsꢀ theꢀ XRDꢀ patternsꢀ ofꢀ theꢀ ZnOꢀ NRAꢀ andꢀ
ZnO‐NRA/C‐xꢀnanohybridsꢀwithꢀdifferentꢀamountsꢀofꢀcarbonꢀ(xꢀ
=ꢀ005,ꢀ01,ꢀ02,ꢀ03).ꢀTheꢀXRDꢀpatternsꢀofꢀbothꢀtheꢀZnOꢀNRAꢀandꢀ
2ꢀcmꢀꢀ2ꢀcmꢀwasꢀusedꢀasꢀtheꢀworkingꢀelectrode.ꢀTheꢀcounterꢀ
electrodeꢀwasꢀplatinumꢀ(Pt)ꢀwire,ꢀandꢀtheꢀreferenceꢀelectrodeꢀ
wasꢀaꢀsilver/silverꢀchlorideꢀ(Ag/AgCl)ꢀelectrode.ꢀPhotocatalyticꢀ
theꢀZnO‐NRA/C‐xꢀnanohybridsꢀwereꢀconsistentꢀwithꢀwell‐crys‐
ꢀ
CO
2
ꢀconversionꢀoverꢀtheꢀZnOꢀNRA/C‐xꢀnanohybridsꢀ(2ꢀcmꢀꢀ3ꢀ
tallizedꢀhexagonalꢀwurtziteꢀZnOꢀ(JCPDSꢀNo.ꢀ361451).ꢀAllꢀsam‐
plesꢀwereꢀnano‐crystalline,ꢀbutꢀtheꢀcrystallinityꢀofꢀtheꢀZnOꢀNRAꢀ
wasꢀhigherꢀthanꢀthoseꢀofꢀtheꢀ ZnO‐NRA/C‐xꢀnanohybrids.ꢀ Theꢀ
crystallinityꢀ ofꢀ theꢀ nanohybridsꢀ decreasedꢀ withꢀ increasingꢀ
amountꢀ ofꢀ glucoseꢀ used.ꢀ Similarꢀ resultsꢀ wereꢀ reportedꢀ byꢀ
Zhangꢀ etꢀ al.ꢀ [25].ꢀ Noꢀ peaksꢀ characteristicꢀ ofꢀ graphiticꢀ carbonꢀ
cm)ꢀwasꢀcarriedꢀoutꢀinꢀaꢀquartzꢀglassꢀreactor,ꢀwhichꢀwasꢀcon‐
nectedꢀtoꢀaꢀclosedꢀgasꢀcirculationꢀandꢀevacuationꢀsystem.ꢀPriorꢀ
toꢀreaction,ꢀ3ꢀmLꢀofꢀdeionizedꢀwaterꢀwasꢀinjectedꢀintoꢀtheꢀre‐
actor.ꢀ Afterꢀ evacuatingꢀ theꢀ reactionꢀ setupꢀ severalꢀ times,ꢀ
high‐purityꢀ CO
2
ꢀ gasꢀ wasꢀ introducedꢀ intoꢀ theꢀ reactionꢀ systemꢀ
untilꢀachievingꢀaꢀpressureꢀofꢀ70ꢀkPa.ꢀThen,ꢀtheꢀCO
2
ꢀphotoreduc‐
wereꢀobservedꢀinꢀtheꢀXRDꢀpatterns,ꢀbecauseꢀofꢀtheꢀnon‐crystal‐
ꢀ
tionꢀreactionꢀwasꢀinitiatedꢀbyꢀexposingꢀtheꢀtopꢀquartzꢀwindowꢀ
ofꢀtheꢀreactorꢀtoꢀvisibleꢀlight.ꢀAtꢀgivenꢀtimeꢀintervals,ꢀ0.5ꢀmLꢀofꢀ
gasꢀwasꢀextractedꢀfromꢀtheꢀreactorꢀusingꢀaꢀprecisionꢀanalyticalꢀ
syringeꢀ(Pressure‐Lok,ꢀUSA)ꢀandꢀwasꢀthenꢀquicklyꢀinjectedꢀintoꢀ
aꢀgasꢀchromatographꢀ(GC‐14B,ꢀShimadzu,ꢀJapan)ꢀequippedꢀwithꢀ
aꢀflameꢀionizedꢀdetectorꢀandꢀmethanizer.ꢀForꢀcomparison,ꢀtheꢀ
lineꢀnatureꢀofꢀcarbonꢀinꢀtheꢀnanohybrids.ꢀRamanꢀspectraꢀofꢀtheꢀ
ZnOꢀ NRA/Cꢀ nanohybridsꢀ showedꢀ twoꢀ peaksꢀ atꢀ aroundꢀ 1351ꢀ
‒1
andꢀ 1597ꢀ cm ꢀ (Fig.ꢀ 1(b)),ꢀ whichꢀ couldꢀ beꢀ assignedꢀ toꢀ theꢀ Dꢀ
bandꢀ andꢀ Gꢀ band,ꢀ respectivelyꢀ [44].ꢀ Noꢀ obviousꢀ peaksꢀ wereꢀ
‒1
observedꢀ atꢀ aroundꢀ 1351ꢀ andꢀ 1597ꢀ cm ꢀ inꢀ theꢀ Ramanꢀ spec‐
trumꢀofꢀtheꢀZnOꢀNRA.ꢀTheꢀappearanceꢀofꢀtheꢀDꢀbandꢀisꢀgeneral‐
lyꢀstrongꢀevidenceꢀforꢀdisorderꢀwithinꢀtheꢀgraphiticꢀstructure,ꢀ
Zn/CꢀfoilꢀsampleꢀwasꢀalsoꢀusedꢀforꢀtheꢀphotoreductionꢀofꢀCO ꢀ
2
2
underꢀidenticalꢀexperimentalꢀconditions.ꢀ
whileꢀ theꢀ Gꢀ bandꢀ indicatesꢀ theꢀ presenceꢀ ofꢀ sp ꢀ carbon‐typeꢀ
structuresꢀ[45].ꢀTheꢀRamanꢀresultsꢀconfirmedꢀtheꢀpresenceꢀofꢀ
graphiticꢀcarbonꢀinꢀtheꢀZnOꢀNRA/Cꢀnanohybrids.ꢀ
3.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
XPSꢀwasꢀusedꢀtoꢀdetermineꢀtheꢀchemicalꢀstateꢀofꢀCꢀatomsꢀinꢀ
theꢀsamples.ꢀTheꢀcoreꢀlevelꢀspectrumꢀinꢀFig.ꢀ2ꢀshowsꢀaꢀbroadꢀ
asymmetricꢀ peak,ꢀ suggestingꢀ theꢀ existenceꢀ ofꢀ moreꢀ thanꢀ oneꢀ
chemicalꢀ stateꢀ ofꢀ C.ꢀTheꢀ Cꢀ1sꢀ spectrumꢀ couldꢀbeꢀ dividedꢀintoꢀ
Schemeꢀ1ꢀillustratesꢀtheꢀprocessꢀusedꢀtoꢀsynthesizeꢀtheꢀZnOꢀ
NRA/C.ꢀFirst,ꢀaꢀwell‐alignedꢀZnOꢀNRAꢀwasꢀgrownꢀdirectlyꢀonꢀaꢀ
zincꢀfoilꢀsubstrateꢀusingꢀaꢀhydrothermalꢀmethodꢀatꢀ180ꢀ°Cꢀforꢀ4ꢀ
Glucose
NaOH&H O2
Immersion
2
Step 1
Step 2
Zinc Foil
Hydrothermal
Carbonization
Schemeꢀ1.ꢀProcessꢀforꢀsynthesizingꢀZnOꢀNRA/C‐xꢀviaꢀaꢀglucose‐assistedꢀtwo‐stepꢀroute.ꢀ(1)ꢀFormationꢀofꢀaꢀZnOꢀNRAꢀviaꢀhydrothermalꢀsynthesisꢀatꢀ
2 2 2
180ꢀ°Cꢀforꢀ4ꢀh,ꢀinꢀaꢀsolutionꢀcontainingꢀ25ꢀmLꢀofꢀH O,ꢀ2ꢀgꢀofꢀNaOH,ꢀandꢀ3.6ꢀmLꢀofꢀ30%ꢀH O ;ꢀ(2)ꢀFormationꢀofꢀZnOꢀNRA/C‐xꢀusingꢀglucoseꢀforꢀcarboni‐
zation,ꢀbyꢀhydrothermalꢀtreatmentꢀandꢀsubsequentꢀcalcinationꢀinꢀargonꢀgasꢀatꢀ800ꢀ°Cꢀforꢀ3ꢀh.ꢀ
(
a)
(b)
ZnO NRA/C-03
ZnO NRA/C-02
ZnO NRA/C-03
ZnO NRA/C-02
ZnO NRA/C-01
ZnO NRA/C-01
ZnO NRA/C-005
ZnO NRA/C-005
ZnO NRA
ZnO NRA
10
20
30
40
2
50

60
70
80
800
1000
1200
1400
1600
1800
2000
1
Raman shift cm 
Fig.ꢀ1.ꢀ(a)ꢀXRDꢀpatternsꢀandꢀ(b)ꢀRamanꢀspectraꢀofꢀtheꢀZnOꢀNRAꢀandꢀZnOꢀNRA/C‐xꢀnanohybrids.ꢀ

976ꢀ
XueweiꢀZhangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ973–981ꢀ
(
a)
(b)
284.8
4
0 nm
5
nm
Carbon
layer
ZnO
2
00 nm
30 nm
286.3
288.4
Fig.ꢀ4.ꢀ(a)ꢀTypicalꢀSEMꢀimageꢀandꢀenlargedꢀimageꢀ(inset)ꢀshowingꢀtheꢀ
characteristicꢀgrowthꢀdirectionꢀ[0001]ꢀofꢀtheꢀZnOꢀ nanorods;ꢀ (b)ꢀTEMꢀ
imageꢀofꢀtheꢀZnOꢀNRA/C‐01ꢀnanohybridꢀandꢀhigh‐resolutionꢀTEMꢀim‐
ageꢀofꢀtheꢀZnOꢀNRAꢀ(inset).ꢀ
282
284
286
Binding energy (eV)
288
290
calculatedꢀtoꢀbeꢀ3.18,ꢀ3.17,ꢀ3.15,ꢀ3.12,ꢀandꢀ3.05ꢀeVꢀforꢀxꢀ=ꢀ0,ꢀ005,ꢀ
0
1,ꢀ 02,ꢀ andꢀ 03,ꢀ respectively.ꢀ Theꢀ bandꢀ gapꢀ energyꢀ decreasedꢀ
Fig.ꢀ2.ꢀCꢀ1sꢀXPSꢀspectrumꢀofꢀZnOꢀNRA/C‐01.ꢀTheꢀsampleꢀwasꢀobtained
byꢀhydrothermalꢀsynthesisꢀinꢀaꢀsolutionꢀofꢀ30ꢀmLꢀofꢀdeionizedꢀwater
andꢀ0.1ꢀgꢀofꢀglucoseꢀatꢀ180ꢀ°Cꢀforꢀ4ꢀh,ꢀfollowedꢀbyꢀcalcinationꢀinꢀargonꢀat
withꢀincreasingꢀamountꢀofꢀincorporatedꢀcarbon.ꢀAsꢀobservedꢀinꢀ
theꢀXPSꢀresults,ꢀtheꢀvisibleꢀlightꢀabsorptionꢀofꢀtheꢀZnOꢀNRA/Cꢀ
nanohybridsꢀcouldꢀbeꢀattributedꢀtoꢀtheꢀdopedꢀcarbonꢀatomsꢀinꢀ
ZnO,ꢀtheꢀCꢀ2pꢀorbitalꢀofꢀwhichꢀformedꢀaꢀnewꢀinter‐bandꢀaboveꢀ
theꢀOꢀ2pꢀorbitalꢀinꢀtheꢀvalenceꢀbandꢀofꢀZnO.ꢀ
800ꢀ°Cꢀforꢀ3ꢀh.ꢀ
threeꢀ peaksꢀ atꢀ 284.8,ꢀ 286.3,ꢀ andꢀ 288.4ꢀ eV,ꢀ correspondingꢀ toꢀ
CC,ꢀCO,ꢀandꢀC=Oꢀbonds,ꢀrespectivelyꢀ[24].ꢀTheꢀbindingꢀenergyꢀ
atꢀ284.8ꢀeVꢀwasꢀdueꢀtoꢀgraphiticꢀcarbonꢀ[39].ꢀTheꢀpeakꢀatꢀ286.3ꢀ
eVꢀsuggestedꢀthatꢀcarbonꢀwasꢀdopedꢀintoꢀtheꢀinterstitialꢀposi‐
tionsꢀofꢀtheꢀZnOꢀlattice,ꢀandꢀformedꢀCOZnꢀbondsꢀwithꢀZnOꢀ
Fig.ꢀ4(a)ꢀshowsꢀaꢀtypicalꢀSEMꢀimageꢀofꢀaꢀZnOꢀNRA.ꢀIndividu‐
alꢀnanorodsꢀhadꢀlengthsꢀofꢀ25ꢀμmꢀandꢀdiametersꢀofꢀ400700ꢀ
nm.ꢀTheꢀenlargedꢀimageꢀ(insetꢀinꢀFig.ꢀ4(a))ꢀshowsꢀthatꢀtheꢀZnOꢀ
nanorodsꢀ wereꢀ grownꢀ alongꢀ theꢀ [0001]ꢀ direction.ꢀ Thisꢀ wasꢀ
evidencedꢀbyꢀtheꢀcharacteristicꢀfeatureꢀofꢀtheirꢀwurtziteꢀstruc‐
ture,ꢀi.e.ꢀthatꢀtheꢀtipꢀofꢀeachꢀnanorodꢀwasꢀconstructedꢀfromꢀsixꢀ
regularꢀ facetsꢀ ofꢀ (103)ꢀ [36].ꢀ TEMꢀ observationsꢀ ofꢀ theꢀ ZnOꢀ
NRA/C‐01ꢀnanohybridꢀshowedꢀthatꢀtheꢀZnOꢀNRAꢀsurfaceꢀwasꢀ
uniformlyꢀcoatedꢀwithꢀanꢀamorphousꢀlayerꢀwithꢀaꢀthicknessꢀofꢀ
aboutꢀ8ꢀnmꢀ(Fig.ꢀ4(b)).ꢀTheꢀRamanꢀ(Fig.ꢀ1(b))ꢀandꢀXPSꢀ(Fig.ꢀ2)ꢀ
analysesꢀcollectivelyꢀindicatedꢀthatꢀtheꢀamorphousꢀcoatingꢀwasꢀ
aꢀ graphiticꢀ carbonꢀ layer.ꢀ Theꢀ intimateꢀ contactꢀ ofꢀ theꢀ carbonꢀ
layerꢀwithꢀtheꢀZnOꢀNRAꢀreportedlyꢀimprovesꢀchargeꢀseparationꢀ
andꢀ thusꢀ photocatalyticꢀ activityꢀ [30,36,47].ꢀ Theꢀ distanceꢀ be‐
tweenꢀneighboringꢀlatticeꢀfringesꢀwasꢀmeasuredꢀtoꢀbeꢀ 0.242ꢀ
nmꢀ fromꢀ theꢀ HRTEMꢀ imageꢀ insetꢀ inꢀ Fig.ꢀ 4(b).ꢀ Thisꢀ wasꢀ veryꢀ
closeꢀtoꢀtheꢀdistanceꢀbetweenꢀtwoꢀadjacentꢀZnOꢀ(002)ꢀcrystalꢀ
planes.ꢀ
[19,27].ꢀ Thisꢀ resultedꢀ inꢀ aꢀ newꢀ inter‐bandꢀ aboveꢀ theꢀ valenceꢀ
bandꢀofꢀZnOꢀ[20],ꢀwhichꢀisꢀdiscussedꢀinꢀmoreꢀdetailꢀbelow.ꢀ
Dopingꢀ orꢀ coatingꢀ ZnOꢀ withꢀ carbonꢀ canꢀ influenceꢀ itsꢀ lightꢀ
absorptionꢀ propertiesꢀ [20,25,37,46].ꢀ Fig.ꢀ 3(a)ꢀ showsꢀ UV‐Visꢀ
diffuseꢀreflectanceꢀspectraꢀofꢀtheꢀsamples.ꢀTheꢀspectrumꢀofꢀtheꢀ
ZnOꢀNRAꢀshowedꢀtheꢀcharacteristicꢀabsorptionꢀedgeꢀofꢀZnOꢀatꢀ
aroundꢀ385ꢀnm.ꢀAfterꢀincorporatingꢀcarbon,ꢀtheꢀZnOꢀNRA/Cꢀ
nanohybridsꢀexhibitedꢀvisibleꢀlightꢀabsorption,ꢀasꢀevidencedꢀbyꢀ
theꢀred‐shiftedꢀabsorptionꢀedgeꢀandꢀtheꢀenhancedꢀbackgroundꢀ
absorptionꢀinꢀtheꢀvisibleꢀregion.ꢀIncreasingꢀtheꢀamountꢀofꢀtheꢀ
carbonꢀcoatingꢀlayerꢀincreasedꢀtheꢀredꢀshiftꢀinꢀabsorptionꢀedgeꢀ
andꢀ alsoꢀ increasedꢀ theꢀ backgroundꢀ absorptionꢀ inꢀ theꢀ visibleꢀ
2
region.ꢀFromꢀtheꢀplotsꢀofꢀ(h) ꢀversusꢀphotonꢀenergyꢀshownꢀinꢀ
Fig.ꢀ3(b),ꢀtheꢀbandꢀgapsꢀofꢀtheꢀZnOꢀNRA/C‐xꢀnanohybridsꢀwereꢀ
(b)
(a)
ZnO NRA
ZnO NRA/C-005
ZnO NRA/C-01
ZnO NRA/C-02
ZnO NRA/C-03
ZnO NRA
ZnO NRA/C-005
ZnO NRA/C-01
ZnO NRA/C-02
ZnO NRA/C-03

360
380
400
420
440
2.8
2.9
3.0
3.1
3.2
3.3
3.4
3.5
Wavelength (nm)
Photon energy (eV)
2
Fig.ꢀ3.ꢀ(a)ꢀUV‐Visꢀdiffuseꢀreflectanceꢀspectraꢀandꢀ(b)ꢀplotsꢀofꢀ(h) ꢀversusꢀphotonꢀenergyꢀofꢀtheꢀZnOꢀNRAꢀandꢀZnOꢀNRA/C‐x.ꢀ

ꢀ
XueweiꢀZhangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ973–981ꢀ
977ꢀ
4
4
3
2
1
800
000
200
400
600
2
2
1
1
0
0
.5 (a)
ZnO NRA/C-01
ZnO NRA
(b)
ZnO NRA
.0
.5
.0
.5
.0
ZnO NRA/C-01
8
00
0
0
20 40 60 80 100 120 140 160 180 200
Time (s)
0
1000
2000
3000
4000
5000
Z' (ohm)
Fig.ꢀ5.ꢀ(a)ꢀTransientꢀphotocurrentꢀresponsesꢀofꢀtheꢀZnOꢀNRAꢀandꢀZnOꢀNRA/C‐01ꢀelectrodesꢀatꢀ0.5ꢀVꢀvs.ꢀAg/AgClꢀunderꢀvisibleꢀlightꢀirradiation;ꢀ(b)ꢀEISꢀ
NyquistꢀplotsꢀofꢀtheꢀZnOꢀNRAꢀandꢀZnOꢀNRA/C‐01ꢀelectrodesꢀatꢀ0.5ꢀVꢀvs.ꢀAg/AgCl,ꢀatꢀfrequenciesꢀofꢀ100105ꢀHz.ꢀ
Toꢀinvestigateꢀtheꢀeffectꢀofꢀcarbonꢀmodificationꢀonꢀtheꢀper‐
formanceꢀofꢀtheꢀZnOꢀNRA,ꢀPECꢀmeasurementsꢀofꢀtheꢀZnOꢀNRAꢀ
andꢀ ZnOꢀ NRA/C‐01ꢀ wereꢀ carriedꢀ out.ꢀ Comparisonꢀ ofꢀ theseꢀ
measurementsꢀ allowedꢀ theꢀ effectꢀ ofꢀ theꢀ interactionꢀ betweenꢀ
theꢀZnOꢀNRAꢀandꢀgraphiticꢀcarbonꢀtoꢀbeꢀprobed.ꢀFig.ꢀ5(a)ꢀshowsꢀ
transientꢀphotoresponsesꢀmeasuredꢀunderꢀvisibleꢀlightꢀirradia‐
creasedꢀ photocatalyticꢀ activity.ꢀ Theꢀ ZnOꢀ NRA/C‐01ꢀ sampleꢀ
exhibitedꢀtheꢀhighestꢀphotocatalyticꢀabilityꢀamongꢀtheꢀfourꢀZnOꢀ
NRA/C‐xꢀnanohybrids.ꢀ Decreasingꢀtheꢀ carbonꢀ coatingꢀ amountꢀ
providedꢀinsufficientꢀprotectionꢀtoꢀtheꢀZnOꢀNRA,ꢀandꢀtheꢀcar‐
bon‐dopingꢀeffectꢀwasꢀinsufficientꢀtoꢀenhanceꢀabsorption.ꢀThus,ꢀ
theꢀlowerꢀamountꢀofꢀincorporatedꢀcarbonꢀresultedꢀinꢀtheꢀlowerꢀ
photocatalyticꢀ activityꢀ ofꢀ theꢀ ZnOꢀ NRA/C‐005ꢀ nanohybrid.ꢀ
Furtherꢀ increasingꢀ theꢀ carbonꢀ coatingꢀ amountꢀ enhancedꢀ theꢀ
visibleꢀlightꢀ absorptionꢀofꢀtheꢀ ZnOꢀNRA/C‐xꢀnanohybrids.ꢀForꢀ
example,ꢀtheꢀZnOꢀNRA/C‐03ꢀsampleꢀexhibitedꢀtheꢀhighestꢀvisi‐
bleꢀlightꢀ absorptionꢀability,ꢀasꢀ shownꢀinꢀFig.ꢀ 3.ꢀTheꢀenhancedꢀ
lightꢀabsorptionꢀmainlyꢀoriginatedꢀfromꢀtheꢀthickꢀcarbonꢀlayerꢀ
coating.ꢀ Anꢀ excessivelyꢀ thickꢀ layerꢀ couldꢀ blockꢀ incidentꢀ lightꢀ
fromꢀtheꢀsurface‐activeꢀsitesꢀofꢀtheꢀZnOꢀNRA,ꢀleadingꢀtoꢀaꢀde‐
creaseꢀinꢀphotocatalyticꢀactivityꢀ[52].ꢀ
2
tion.ꢀ Theꢀ photocurrentꢀ ofꢀ ZnOꢀ NRA/C‐01ꢀ (2.2ꢀ A/cm )ꢀ wasꢀ
2
aboutꢀ4.4ꢀtimesꢀhigherꢀthanꢀthatꢀofꢀtheꢀZnOꢀNRAꢀ(0.5ꢀA/cm ),ꢀ
whichꢀ indicatedꢀ theꢀ efficientꢀ electron‐holeꢀ separationꢀ inꢀ ZnOꢀ
NRA/C‐01.ꢀElectrochemicalꢀimpedanceꢀspectroscopyꢀ(EIS)ꢀwasꢀ
usedꢀtoꢀelucidateꢀtheꢀchargeꢀtransferꢀbehaviorꢀ(i.e.,ꢀseparationꢀ
efficiencyꢀofꢀchargeꢀcarriers)ꢀinꢀtheꢀsamples.ꢀTheꢀEISꢀNyquistꢀ
plotsꢀ inꢀ Fig.ꢀ 5(b)ꢀ showꢀ thatꢀ theꢀ semicircleꢀ ofꢀ ZnOꢀ NRA/C‐01ꢀ
wasꢀ muchꢀ smallerꢀ thanꢀ thatꢀ ofꢀ theꢀ ZnOꢀ NRA.ꢀ Thisꢀ indicatedꢀ
moreꢀefficientꢀinterfacialꢀelectronꢀtransferꢀinꢀZnOꢀNRA/C‐01,ꢀasꢀ
aꢀ resultꢀ ofꢀ theꢀ existenceꢀ ofꢀ carbonꢀ [48].ꢀ Carbonꢀ modificationꢀ
significantlyꢀenhancedꢀtheꢀseparationꢀandꢀtransportꢀofꢀphoto‐
generatedꢀ chargeꢀ carriersꢀ inꢀ theꢀ ZnOꢀ NRA/C‐01ꢀ nanohybridꢀ
Toꢀ confirmꢀ theꢀ repeatabilityꢀ andꢀ stabilityꢀ ofꢀ theꢀ ZnOꢀ
NRA/C‐xꢀnanohybrids,ꢀfourꢀconsecutiveꢀrunsꢀofꢀtheꢀphotocata‐
lyticꢀCO
ꢀreductionꢀoverꢀtheꢀZnOꢀNRA/C‐01ꢀnanohybridꢀwereꢀ
2
[
36,39].ꢀ
carriedꢀ outꢀ underꢀ visibleꢀ lightꢀ irradiation.ꢀ Afterꢀ eachꢀ 5‐hourꢀ
run,ꢀtheꢀlightꢀwasꢀturnedꢀoffꢀandꢀtheꢀphotoreactorꢀwasꢀevacu‐
Efficientꢀchargeꢀseparationꢀisꢀimportantꢀforꢀenhancedꢀpho‐
tocatalyticꢀactivityꢀ[33,49,50].ꢀPLꢀmeasurementsꢀwereꢀusedꢀtoꢀ
furtherꢀinvestigateꢀtheꢀtransferꢀbehaviorꢀofꢀphotoinducedꢀelec‐
trons.ꢀ Fig.ꢀ 6ꢀ showsꢀ PLꢀ spectraꢀ ofꢀ theꢀ ZnOꢀ NRAꢀ andꢀ ZnOꢀ
NRA/C‐01ꢀnanohybrid,ꢀexcitedꢀatꢀaꢀwavelengthꢀofꢀ275ꢀnm.ꢀTheꢀ
PLꢀintensityꢀofꢀZnOꢀNRA/C‐01ꢀwasꢀsignificantlyꢀlowerꢀthanꢀthatꢀ
ofꢀtheꢀZnOꢀNRA,ꢀbecauseꢀofꢀtheꢀquenchingꢀeffectꢀofꢀtheꢀcarbonꢀ
layerꢀ coatingꢀ theꢀ ZnOꢀ NRA.ꢀ Theꢀ quenchingꢀ effectꢀ inꢀ ZnOꢀ
NRA/C‐01ꢀresultedꢀinꢀtheꢀrapidꢀtransferꢀofꢀphotoelectronsꢀfromꢀ
theꢀZnOꢀNRAꢀtoꢀtheꢀcarbonꢀlayer.ꢀInꢀotherꢀwords,ꢀtheꢀcarbonꢀ
layerꢀcoatedꢀonꢀtheꢀZnOꢀNRAꢀsuppressedꢀtheꢀrecombinationꢀofꢀ
photoinducedꢀchargeꢀcarriersꢀ[51],ꢀthusꢀenhancingꢀtheꢀphoto‐
catalyticꢀactivityꢀofꢀZnOꢀNRA/C‐01.ꢀ
ZnO NRA
ZnO NRA/C-01
PhotocatalyticꢀCO
ꢀreductionꢀwasꢀcarriedꢀoutꢀoverꢀtheꢀZnOꢀ
2
NRA/C‐xꢀnanohybridsꢀandꢀZnOꢀNRAꢀunderꢀvisibleꢀlightꢀirradia‐
tion.ꢀFig.ꢀ7ꢀshowsꢀthatꢀtheꢀactivitiesꢀofꢀallꢀtheꢀZnOꢀNRA/C‐xꢀna‐
3
30
360
390
420
450
nohybridsꢀforꢀevolvingꢀCH ꢀand/orꢀCOꢀwereꢀhigherꢀthanꢀthoseꢀ
4
Wavelength (nm)
ofꢀtheꢀZnOꢀNRA.ꢀAsꢀdiscussedꢀabove,ꢀrapidꢀtransferꢀofꢀphotoe‐
lectronsꢀfromꢀtheꢀZnOꢀNRAꢀtoꢀtheꢀcarbonꢀlayerꢀoccurredꢀinꢀtheꢀ
ZnOꢀ NRA/C‐xꢀ nanohybrids,ꢀ whichꢀ couldꢀ accountꢀ forꢀ theꢀ in‐
Fig.ꢀ6.ꢀPLꢀspectraꢀofꢀtheꢀZnOꢀNRA/C‐01ꢀnanohybridꢀandꢀZnOꢀNRAꢀatꢀ
roomꢀtemperature.ꢀ

978ꢀ
XueweiꢀZhangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ973–981ꢀ
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0.9
(
b)
(3)
(2)
(a)
(
3)
0.8
(
1) ZnO NRA
(2) ZnO NRA/C-005
3) ZnO NRA/C-01
(4) ZnO NRA/C-02
5) ZnO NRA/C-03
(1) ZnO NRA
0.7
0.6
0.5
0.4
(2) ZnO NRA/C-005
(3) ZnO NRA/C-01
(4) ZnO NRA/C-02
(5) ZnO NRA/C-03
(
(
2)
(
(4)
(
4)
(
5)
1)
(
(
5)
1)
0.3
(
0
.2
.1
0
0.0
0
1
2
3
4
5
6
0
1
2
3
4
5
6
Irradiation time (h)
Irradiation time (h)
ꢀandꢀ(b)ꢀCOꢀevolutionꢀoverꢀZnOꢀNRAꢀandꢀZnOꢀNRA/C‐xꢀ(xꢀ=ꢀ005,ꢀ01,ꢀ02,ꢀandꢀ03)ꢀasꢀaꢀfunctionꢀofꢀirradiationꢀtimeꢀunderꢀvisibleꢀlight.ꢀ
Fig.ꢀ7.ꢀ(a)ꢀCH
4
atedꢀbeforeꢀrefillingꢀwithꢀCO
thereꢀwereꢀnoꢀobviousꢀdecreasesꢀinꢀtheꢀyieldsꢀofꢀCH
afterꢀfourꢀruns,ꢀwhichꢀdemonstratedꢀtheꢀstableꢀphotocatalyticꢀ
activityꢀofꢀtheꢀZnOꢀNRA/C‐01ꢀnanohybrid.ꢀFurtherꢀXPSꢀmeas‐
urementsꢀofꢀtheꢀOꢀ1sꢀspectrumꢀofꢀZnOꢀNRA/C‐01ꢀshowedꢀthatꢀ
2
ꢀandꢀH
2
Oꢀ(3ꢀmL).ꢀFig.ꢀ8ꢀshowsꢀthatꢀ
structuresꢀ [54],ꢀ theꢀ photoactivityꢀ andꢀ photostabilityꢀ ofꢀ whichꢀ
wereꢀimprovedꢀbyꢀcoatingꢀwithꢀaꢀTiO ꢀlayer.ꢀ
Weꢀthenꢀcarriedꢀoutꢀaꢀseriesꢀofꢀcontrolꢀexperimentsꢀtoꢀclari‐
fyꢀ theꢀ reactionꢀ mechanismꢀ ofꢀ CO ꢀ photoreductionꢀ withꢀ H Oꢀ
overꢀtheꢀZnOꢀNRA/C‐01ꢀnanohybrid.ꢀWhenꢀtheꢀexperimentꢀwasꢀ
performedꢀinꢀtheꢀdarkꢀorꢀinꢀtheꢀabsenceꢀofꢀtheꢀphotocatalyst,ꢀ
4
ꢀandꢀCOꢀ
2
2
2
theꢀamountsꢀofꢀsurfaceꢀlatticeꢀOꢀandꢀOHꢀdecreased,ꢀwhileꢀtheꢀ

amountsꢀofꢀadsorbedꢀ•O
2
ꢀspeciesꢀincreasedꢀandꢀtheꢀassociatedꢀ
COꢀandꢀCH
andꢀ theꢀ photocatalystꢀ wereꢀ requiredꢀ toꢀ generateꢀ COꢀ and/orꢀ
CH .ꢀ Weꢀ performedꢀ anotherꢀ controlꢀ experimentꢀ byꢀ replacingꢀ
CO ꢀwithꢀpureꢀArꢀgas,ꢀwhileꢀkeepingꢀtheꢀsameꢀamountꢀofꢀH Oꢀinꢀ
theꢀreactor.ꢀOnlyꢀaꢀtraceꢀamountꢀofꢀhydrogenꢀfromꢀwaterꢀsplit‐
tingꢀwasꢀdetected,ꢀimplyingꢀthatꢀtheꢀCꢀandꢀHꢀsourcesꢀwereꢀCO
andꢀ H O,ꢀ respectively.ꢀ Inꢀ yetꢀ anotherꢀ controlꢀ experiment,ꢀ aꢀ
Zn/Cꢀ foilꢀ sampleꢀ (i.e.,ꢀ Znꢀ foilꢀ coatedꢀ withꢀ aꢀ graphiticꢀ carbonꢀ
layer)ꢀwasꢀpreparedꢀforꢀCO ꢀphotoreductionꢀunderꢀsimilarꢀex‐
perimentalꢀconditions.ꢀCH ꢀandꢀCOꢀcouldꢀnotꢀbeꢀdetected,ꢀwhichꢀ
4
ꢀcouldꢀnotꢀbeꢀdetected.ꢀThisꢀindicatedꢀthatꢀbothꢀlightꢀ
XPSꢀpeaksꢀshiftedꢀtoꢀlowerꢀenergy,ꢀasꢀtheꢀreactionꢀproceeded.ꢀItꢀ
wasꢀ believedꢀ thatꢀ surfaceꢀ latticeꢀ Oꢀ andꢀ –OHꢀ wereꢀ convertedꢀ
4

intoꢀ •O
2
ꢀ duringꢀ theꢀ photoreaction.ꢀ Thereꢀ wasꢀ veryꢀ littleꢀ dif‐
2
2
ferenceꢀ inꢀ theꢀ profileꢀ ofꢀ theꢀ Oꢀ 1sꢀ XPSꢀ spectrumꢀ ofꢀ theꢀ ZnOꢀ
NRA/C‐01ꢀ nanohybridꢀ beforeꢀ andꢀ afterꢀ reactionꢀ (dataꢀ notꢀ
shown),ꢀwhichꢀindicatedꢀtheꢀhighꢀstabilityꢀofꢀtheꢀZnOꢀNRA/C‐xꢀ
nanohybridsꢀduringꢀtheꢀphotocatalyticꢀreaction.ꢀInꢀcomparison,ꢀ
aꢀ similarꢀ testꢀ conductedꢀ onꢀ theꢀ ZnOꢀ NRAꢀ sampleꢀ showedꢀ anꢀ
obviousꢀdecreaseꢀinꢀtheꢀphotoactivityꢀafterꢀreactionꢀforꢀ5ꢀh.ꢀTheꢀ
above‐mentionedꢀ resultsꢀ demonstratedꢀ thatꢀ theꢀ photocorro‐
sionꢀand/orꢀoxidationꢀofꢀtheꢀZnOꢀNRAꢀwereꢀinhibited.ꢀThisꢀwasꢀ
attributedꢀtoꢀtheꢀprotectionꢀprovidedꢀbyꢀtheꢀsuitablyꢀthickꢀcar‐
bonꢀ layerꢀ coatedꢀ onꢀ theꢀ ZnOꢀ NRA.ꢀ Similarꢀ observationsꢀ haveꢀ
2
ꢀ
2
2
4
4
excludedꢀtheꢀpossibilityꢀofꢀCH ꢀand/orꢀCOꢀoriginatingꢀfromꢀtheꢀ
graphiticꢀcarbon.ꢀ
Basedꢀonꢀtheꢀaboveꢀexperimentalꢀresultsꢀandꢀdiscussion,ꢀweꢀ
proposeꢀaꢀmechanismꢀforꢀtheꢀphotocatalyticꢀCO ꢀreductionꢀoverꢀ
theꢀZnOꢀNRA/C‐xꢀnanohybridsꢀ(Schemeꢀ2).ꢀUponꢀlightꢀirradia‐
2
beenꢀreportedꢀforꢀTiO
2
ꢀnanolayer/CdSꢀnanorodꢀarrayꢀ[53]ꢀandꢀ


2
TiO ꢀ nanolayer/CdS‐sensitizedꢀ ZnOꢀ nanorodꢀ arrayꢀ compositeꢀ
tion,ꢀelectron/holeꢀ(e /h )ꢀpairsꢀareꢀgeneratedꢀonꢀtheꢀsurfaceꢀofꢀ
theꢀ ZnOꢀ NRA.ꢀ Theꢀ electronsꢀ quicklyꢀ transferꢀ toꢀ theꢀ graphiticꢀ
0.8
0.6
0.4
0.2
0.0
carbonꢀlayer,ꢀinitiatingꢀtheꢀreductionꢀofꢀCO
CH ,ꢀ andꢀ H .ꢀ Theꢀ holesꢀ remainingꢀ atꢀ theꢀ valenceꢀ bandꢀ ofꢀ theꢀ
ZnOꢀ NRAꢀ areꢀ supposedꢀ toꢀ oxidizeꢀ water.ꢀ Experimentally,ꢀ weꢀ
didꢀnotꢀdetectꢀtheꢀexpectedꢀoxidativeꢀproductꢀO .ꢀMostꢀlikely,ꢀ
2
ꢀwithꢀH OꢀintoꢀCO,ꢀ
2
4
2
2
CO
CO
CO
CO
CH
theꢀ oxidativeꢀ productꢀ preferentiallyꢀ adoptedꢀ theꢀ stateꢀ ofꢀ ab‐

sorbedꢀ •O
2
ꢀ inꢀ theꢀ formꢀ ofꢀ –Zn–O–O–Zn–ꢀ [47].ꢀ Toꢀ clarifyꢀ theꢀ
ꢀ reductionꢀ overꢀ theꢀ ZnOꢀ
mechanismꢀ ofꢀ theꢀ photocatalyticꢀ CO
2
NRA/C‐xꢀnanohybrids,ꢀfurtherꢀexperimentsꢀneedꢀtoꢀbeꢀcarriedꢀ
outꢀtoꢀdetectꢀproductsꢀinꢀtheꢀliquidꢀphase.ꢀTheseꢀexperimentsꢀ
willꢀformꢀpartꢀofꢀourꢀfutureꢀstudies.ꢀ
CH
4
CH
4
CH
4
4
Theꢀ photocatalyticꢀ reductionꢀ ofꢀ chemicallyꢀ stableꢀ CO ꢀ isꢀ aꢀ
2
complexꢀ processꢀ involvingꢀ C=Oꢀ covalentꢀ bondꢀ breakingꢀ andꢀ
CH/CCꢀbondꢀformationꢀ[5,26,55].ꢀTheꢀZnOꢀNRA/C‐xꢀnanohy‐
bridꢀ photocatalystꢀ possessesꢀ severalꢀ advantagesꢀ forꢀ photo‐
0
5
10
15
20
Irradiation time (h)
2
catalyticꢀ CO ꢀreduction.ꢀ Theseꢀ includeꢀfavorableꢀballisticꢀelec‐
Fig.ꢀ 8.ꢀ Consecutiveꢀ runsꢀ forꢀ theꢀ photoreductionꢀ ofꢀ CO ꢀ overꢀ theꢀ ZnO
2
NRA/C‐01ꢀnanohybridꢀunderꢀvisibleꢀlightꢀirradiation.ꢀ
tronꢀtransportꢀcapabilityꢀinꢀtheꢀ1‐DꢀZnOꢀnanorods.ꢀOnꢀtheꢀZnOꢀ

ꢀ
XueweiꢀZhangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ973–981ꢀ
979ꢀ
photocatalyticꢀactivityꢀofꢀtheꢀZnOꢀNRA/C‐xꢀnanohybridsꢀforꢀCO
ꢀ
2
Vac.
E(eV)
reductionꢀ wasꢀ improved.ꢀ Theseꢀ findingsꢀ demonstrateꢀ thatꢀ
graphiticꢀcarbonꢀmediationꢀisꢀanꢀeffectiveꢀandꢀfeasibleꢀwayꢀtoꢀ
improveꢀtheꢀphotostability,ꢀchargeꢀcarrierꢀseparation,ꢀabsorp‐
tionꢀrange,ꢀandꢀphotocatalyticꢀactivityꢀofꢀsemiconductor‐basedꢀ
photocatalysts.ꢀ
Graphitic carbon
ZnO NRAs/C-x
H

 
e e e

CB(ZnO) e e
CO + CH4
/CH
CO
2
4
2 2
O /H O
Referencesꢀ
+
+
+
h h h
+
O + H
2
C-doping level
[
1] A.ꢀFujishima,ꢀK.ꢀHonda,ꢀNature,ꢀ1972,ꢀ238,ꢀ37–38.ꢀ
H O
2
VB(ZnO)
[2] Z.ꢀ G.ꢀ Zou,ꢀ J.H.ꢀ Ye,ꢀ K.ꢀ Sayama,ꢀ H.ꢀ Arakawa,ꢀ Nature,ꢀ 2001,ꢀ 414,ꢀ
625–627.ꢀ
[
3] M.ꢀHalmann,ꢀNature,ꢀ1978,ꢀ275,ꢀ115–116.ꢀ
Schemeꢀ2.ꢀSchematicꢀofꢀtheꢀmechanismꢀofꢀtheꢀphotocatalyticꢀconver‐
sionꢀofꢀCO ꢀintoꢀCOꢀand/orꢀCH ꢀoverꢀtheꢀZnOꢀNRA/C‐xꢀnanohybrids.ꢀ
[4] D.ꢀF.ꢀWang,ꢀA.ꢀPierre,ꢀM.ꢀG.ꢀKibria,ꢀK.ꢀCui,ꢀX.ꢀG.ꢀHan,ꢀK.ꢀH.ꢀBevan,ꢀH.ꢀ
Guo,ꢀ S.ꢀ Paradis,ꢀ A.ꢀ R.ꢀ Hakima,ꢀ Z.ꢀ T.ꢀ Mi,ꢀ Nanoꢀ Lett.,ꢀ 2011,ꢀ 11,ꢀ
2
4
2
353–2357.ꢀ
NRAꢀ surface,ꢀ theꢀ graphiticꢀ carbonꢀ layerꢀ furtherꢀ enhancesꢀ
chargeꢀ carrierꢀ separation.ꢀ Inꢀ addition,ꢀ theꢀ dopedꢀ Cꢀ 2pꢀ levelꢀ
aboveꢀtheꢀOꢀ2pꢀorbitalꢀinꢀtheꢀvalenceꢀbandꢀextendsꢀtheꢀabsorp‐
tionꢀ ofꢀ theꢀ ZnOꢀ NRA/C‐xꢀnanohybridsꢀintoꢀtheꢀvisibleꢀregion.ꢀ
Theseꢀ advantagesꢀ resultꢀ inꢀ theꢀ ZnOꢀ NRA/C‐xꢀ nanohybridsꢀ
showingꢀfavorableꢀphotocatalyticꢀactivity,ꢀinꢀtermsꢀofꢀbothꢀbandꢀ
engineeringꢀ(carbonꢀdopingꢀeffect)ꢀandꢀphotoreactionꢀkineticsꢀ
[
5] A.ꢀSarkar,ꢀE.ꢀGracia‐Espino,ꢀT.ꢀWågberg,ꢀA.ꢀShchukarev,ꢀM.ꢀMohl,ꢀA.ꢀ
R.ꢀRautio,ꢀO.ꢀPitkänen,ꢀT.ꢀSharifi,ꢀK.ꢀKordas,ꢀJ.ꢀP.ꢀMikkola,ꢀNanoꢀRes.,ꢀ
2
016,ꢀ9,ꢀ1956–1968.ꢀ
[6] M.ꢀ Marszewski,ꢀ S.ꢀ W.ꢀ Cao,ꢀ J.ꢀ G.ꢀ Yu,ꢀ M.ꢀ Jaroniec,ꢀ Mater.ꢀ Horizons,ꢀ
2015,ꢀ2,ꢀ261–278
.
[7] Q.ꢀ J.ꢀ Xiang,ꢀ B.ꢀ Cheng,ꢀ J.ꢀ G.ꢀ Yu,ꢀ Angew.ꢀ Chem.ꢀ Int.ꢀ Ed.,ꢀ 2015,ꢀ 54,ꢀ
11350–11366.ꢀ
[
8] J.ꢀX.ꢀLow,ꢀB.ꢀCheng,ꢀJ.ꢀG.ꢀYu,ꢀAppl.ꢀSurf.ꢀSci.,ꢀ2017,ꢀ392,ꢀ658–686.ꢀ
9] G.ꢀ S.ꢀ Li,ꢀ D.ꢀ Q.ꢀ Zhang,ꢀ J.ꢀ C.ꢀ Yu,ꢀ Environ.ꢀ Sci.ꢀ Technol.,ꢀ 2009,ꢀ 43,ꢀ
(
chargeꢀcarrierꢀseparationꢀandꢀtransport).ꢀ
.ꢀ ꢀ Conclusionsꢀ
Weꢀ synthesizedꢀ graphitic‐carbon‐mediatedꢀ visible‐light‐
[
7079–7085.ꢀ
4
[
10] G.ꢀHitoki,ꢀT.ꢀTakata,ꢀJ.ꢀN.ꢀKondo,ꢀM.ꢀHara,ꢀH.ꢀKobayashi,ꢀK.ꢀDomen,ꢀ
Chem.ꢀCommun.,ꢀ2002,ꢀ1698–1699.ꢀ
11] X.ꢀWei,ꢀT.ꢀF.ꢀXie,ꢀL.ꢀL.ꢀPeng,ꢀW.ꢀFu,ꢀJ.ꢀS.ꢀChen,ꢀQ.ꢀGao,ꢀG.Y.ꢀHong,ꢀD.ꢀJ.ꢀ
Wang,ꢀJ.ꢀPhys.ꢀChem.ꢀC,ꢀ2011,ꢀ115,ꢀ8637–8642.ꢀ
12] Y.ꢀP.ꢀBi,ꢀJ.ꢀH.ꢀYe,ꢀChem.ꢀCommun.,ꢀ2009,ꢀ6551–6553.ꢀ
13] E.ꢀ Reisner,ꢀ D.ꢀ J.ꢀ Powell,ꢀ C.ꢀ Cavazza,ꢀ J.ꢀ C.ꢀ Fontecilla‐Camps,ꢀ F.ꢀ A.ꢀ
Armstrong,ꢀJ.ꢀAm.ꢀChem.ꢀSoc.,ꢀ2009,ꢀ131,ꢀ18457–18466.ꢀ
14] Y.ꢀ J.ꢀ Wang,ꢀ R.ꢀ Shi,ꢀ J.ꢀ Lin,ꢀ Y.ꢀ F.ꢀ Zhu,ꢀ EnergyꢀEnviron.ꢀSci.,ꢀ 2011,ꢀ4,ꢀ
ꢀ
re‐
[
sponsiveꢀZnOꢀNRA/C‐xꢀonꢀzincꢀfoilꢀviaꢀaꢀmodifiedꢀhydrothermalꢀ
method.ꢀ Byꢀ calciningꢀ theꢀ pre‐synthesizedꢀ ZnOꢀ NRAsꢀ andꢀ dif‐
ferentꢀamountsꢀofꢀglucoseꢀasꢀaꢀcarbonꢀsourceꢀatꢀaꢀsuitableꢀhy‐
drothermalꢀ temperature,ꢀ weꢀ obtainedꢀ ZnOꢀ NRA/C‐xꢀ nanohy‐
brids.ꢀComparedꢀwithꢀtheꢀZnOꢀNRA,ꢀtheꢀnanohybridsꢀexhibitedꢀ
increasedꢀopticalꢀabsorptionꢀandꢀphotostabilityꢀdueꢀtoꢀtheꢀcar‐
bon‐dopingꢀandꢀcarbon‐coatingꢀeffects.ꢀChargeꢀcarrierꢀsepara‐
tionꢀ andꢀ transportꢀ inꢀ theꢀ ZnOꢀ NRA/C‐xꢀ nanohybridsꢀ wasꢀ en‐
hancedꢀcomparedꢀwithꢀinꢀtheꢀZnOꢀNRA,ꢀbecauseꢀofꢀtheꢀgraphiticꢀ
carbonꢀlayerꢀcoatedꢀonꢀtheꢀZnOꢀNRAꢀsurface.ꢀAsꢀaꢀresult,ꢀtheꢀ
[
[
[
2922–2929.ꢀ
[
15] B.ꢀA.ꢀParkinson,ꢀP.ꢀF.ꢀWeaver,ꢀNature,ꢀ1984,ꢀ309,ꢀ148–149.ꢀ
[16] L.ꢀL.ꢀYin,ꢀM.ꢀZhao,ꢀH.ꢀL.ꢀHu,ꢀJ.ꢀH.ꢀYe,ꢀD.ꢀF.ꢀWang,ꢀChin.ꢀJ.ꢀCatal.,ꢀ2017,ꢀ
38,ꢀ1307–1314.ꢀ
[17] H.ꢀBouzid,ꢀM.ꢀFaisal,ꢀF.ꢀA.ꢀHarraz,ꢀS.ꢀA.ꢀAl‐Sayari,ꢀA.ꢀA.ꢀIsmail,ꢀCatal.ꢀ
GraphicalꢀAbstractꢀ
Chin.ꢀJ.ꢀCatal.,ꢀ2018,ꢀ39:ꢀ973–981ꢀ ꢀ ꢀ doi:ꢀ10.1016/S1872‐2067(18)63010‐4
Enhancingꢀtheꢀphotocatalyticꢀactivityꢀandꢀphotostabilityꢀofꢀ
zincꢀoxideꢀnanorodꢀarraysꢀviaꢀgraphiticꢀcarbonꢀmediationꢀ
-2
E (eV)/Vac.
CO + H O
CO + CH4
-3
2
2
XueweiꢀZhang,ꢀXueliangꢀZhang,ꢀXinꢀWang,ꢀLequanꢀLiu,ꢀJinhuaꢀYe,ꢀ
DefaꢀWangꢀ*ꢀ
TianjinꢀUniversity,ꢀChina;ꢀ ꢀ
CO + CH
+ H
CO /CH
4
e
e
CB (ZnO)
-
4
CO
2
CollaborativeꢀInnovationꢀCenterꢀofꢀChemicalꢀScienceꢀandꢀ ꢀ
Engineeringꢀ(Tianjin),ꢀChina;ꢀ ꢀ
NationalꢀInstituteꢀforꢀMaterialsꢀScience,ꢀJapanꢀ
2
4
Graphitic carbon
-5
h
2 2
H O/O
-
-
6
7
Graphitic‐carbon‐mediatedꢀZnOꢀnanorodꢀarraysꢀ(NRAs)ꢀareꢀfabri‐
catedꢀ byꢀ calciningꢀ pre‐synthesizedꢀ ZnOꢀ NRAsꢀ withꢀ differentꢀ
amountsꢀofꢀglucoseꢀasꢀaꢀcarbonꢀsource,ꢀviaꢀaꢀhydrothermalꢀmeth‐
od.ꢀ Theꢀ resultingꢀ nanohybridsꢀ exhibitꢀ enhancedꢀ photocatalyticꢀ
C-doping level
2
H O
h+
VB (ZnO)
+
O2 + H
2
activityꢀ andꢀ photostabilityꢀ forꢀ CO ꢀ reductionꢀ underꢀ visibleꢀ lightꢀ
irradiation.ꢀ
-8

980ꢀ
XueweiꢀZhangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ973–981ꢀ
Today,ꢀ2015,ꢀ252,ꢀ20–26.ꢀ
18] W.ꢀL.ꢀYu,ꢀJ.ꢀF.ꢀZhang,ꢀT.ꢀY.ꢀPeng,ꢀAppl.ꢀCatal.ꢀB,ꢀ2016,ꢀ181,ꢀ220–227.ꢀ
19] M.ꢀJ.ꢀZhou,ꢀX.ꢀH.ꢀGao,ꢀY.ꢀHu,ꢀJ.ꢀF.ꢀChen,ꢀX.ꢀHu,ꢀAppl.ꢀCatal.ꢀB,ꢀ2013,ꢀ
Chen,ꢀY.ꢀC.ꢀLiu,ꢀACSꢀAppl.ꢀMater.ꢀInterfaces,ꢀ2011,ꢀ3,ꢀ590–596.ꢀ
[37] C.ꢀHan,ꢀM.ꢀQ.ꢀYang,ꢀB.ꢀWeng,ꢀY.ꢀJ.ꢀXu,ꢀPhys.ꢀChem.ꢀChem.ꢀPhys.,ꢀ2014,ꢀ
16,ꢀ16891–16903.ꢀ
[
[
1
38–139,ꢀ1–8.ꢀ
20] S.ꢀT.ꢀKochuveedu,ꢀY.ꢀH.ꢀJang,ꢀY.ꢀJ.ꢀJang,ꢀD.ꢀH.ꢀKim,ꢀJ.ꢀMater.ꢀChem.ꢀA,ꢀ
013,ꢀ1,ꢀ898–905.ꢀ
[38] Y.ꢀGuo,ꢀH.ꢀS.ꢀWang,ꢀC.ꢀL.ꢀHe,ꢀL.ꢀJ.ꢀQiu,ꢀX.ꢀB.ꢀCao,ꢀLangmuir,ꢀ2009,ꢀ25,ꢀ
4678–4684.ꢀ
[39] H.ꢀYu,ꢀH.C.ꢀZhang,ꢀH.ꢀHuang,ꢀY.ꢀLiu,ꢀH.ꢀT.ꢀLi,ꢀH.ꢀMing,ꢀZ.ꢀH.ꢀKang,ꢀNewꢀ
J.ꢀChem.,ꢀ2012,ꢀ36,ꢀ1031–1035.ꢀ
[
[
2
21] J.ꢀShim,ꢀJ.ꢀK.ꢀKim,ꢀK.ꢀS.ꢀLee,ꢀC.ꢀL.ꢀLee,ꢀM.ꢀMa,ꢀW.ꢀK.ꢀChoi,ꢀJ.ꢀY.ꢀHwang,ꢀ
H.ꢀY.ꢀYang,ꢀB.ꢀAngadi,ꢀJ.ꢀH.ꢀPark,ꢀK.ꢀYu,ꢀD.ꢀI.ꢀSon,ꢀNanoꢀEnergy,ꢀ2016,ꢀ
[40] S.ꢀAkir,ꢀA.ꢀHamdi,ꢀA.ꢀAddad,ꢀY.ꢀCoffinier,ꢀR.ꢀBoukherroub,ꢀA.ꢀDakh‐
laouiꢀOmrani,ꢀAppl.ꢀSurf.ꢀSci.,ꢀ2017,ꢀ400,ꢀ461–470.ꢀ
[41] J.ꢀQ.ꢀQin,ꢀX.ꢀY.ꢀZhang,ꢀY.ꢀN.ꢀXue,ꢀN.ꢀKittiwattanothai,ꢀP.ꢀKongsittikul,ꢀ
N.ꢀRodthongkum,ꢀS.ꢀLimpanart,ꢀM.ꢀZ.ꢀMa,ꢀR.ꢀP.ꢀLiu,ꢀAppl.ꢀSurf.ꢀSci.,ꢀ
2014,ꢀ321,ꢀ226–232.ꢀ
[42] Y.ꢀG.ꢀPeng,ꢀJ.ꢀL.ꢀJi,ꢀD.ꢀJ.ꢀChen,ꢀAppl.ꢀSurf.ꢀSci.,ꢀ2015,ꢀ356,ꢀ762–768.ꢀ
[43] Q.ꢀTang,ꢀW.ꢀJ.ꢀZhou,ꢀJ.ꢀM.ꢀShen,ꢀW.ꢀZhang,ꢀL.ꢀF.ꢀKong,ꢀY.ꢀT.ꢀQian,ꢀ
Chem.ꢀCommun.,ꢀ2004,ꢀ712–713.ꢀ
2
5,ꢀ9–17.ꢀ
22] H.ꢀB.ꢀFu,ꢀT.ꢀG.ꢀXu,ꢀS.ꢀB.ꢀZhu,ꢀY.ꢀF.ꢀZhu,ꢀEnviron.ꢀSci.ꢀTechnol.,ꢀ2008,ꢀ
2,ꢀ8064–8069.ꢀ
23] L.ꢀ W.ꢀ Zhang,ꢀ H.ꢀ Y.ꢀ Cheng,ꢀ R.ꢀ L.ꢀ Zong,ꢀ Y.ꢀ F.ꢀ Zhu,ꢀ J.ꢀ Phys.ꢀ Chem.ꢀ C,ꢀ
009,ꢀ113,ꢀ2368–2374.ꢀ
24] H.ꢀ Zhang,ꢀ R.ꢀ L.ꢀ Zong,ꢀ Y.ꢀ F.ꢀ Zhu,ꢀ J.ꢀ Phys.ꢀ Chem.ꢀ C,ꢀ 2009,ꢀ 113,ꢀ
605–4611.ꢀ
[
[
[
[
4
2
4
25] X.ꢀY.ꢀZhang,ꢀJ.ꢀQ.ꢀQin,ꢀR.ꢀR.ꢀHao,ꢀL.ꢀM.ꢀWang,ꢀX.ꢀShen,ꢀR.ꢀC.ꢀYu,ꢀ S.ꢀ
[44] P.ꢀC.ꢀEklund,ꢀJ.ꢀM.ꢀHolden,ꢀR.ꢀA.ꢀJishi,ꢀCarbon,ꢀ1995,ꢀ33,ꢀ959–972.ꢀ
[45] D.ꢀR.ꢀDreyer,ꢀS.ꢀPark,ꢀC.ꢀW.ꢀBielawski,ꢀR.ꢀS.ꢀRuoff,ꢀChem.ꢀSoc.ꢀRev.,ꢀ
2010,ꢀ39,ꢀ228–240.ꢀ
Limpanart,ꢀ M.ꢀ Z.ꢀ Ma,ꢀ R.ꢀ P.ꢀ Liu,ꢀ J.ꢀ Phys.ꢀ Chem.ꢀ C,ꢀ 2015,ꢀ 119,ꢀ
20544–20554.ꢀ
[
26] S.ꢀW.ꢀLiu,ꢀJ.ꢀH.ꢀWang,ꢀJ.ꢀG.ꢀYu,ꢀRSCꢀAdv.,ꢀ2016,ꢀ6,ꢀ59998–60006.ꢀ
27] F.ꢀX.ꢀWang,ꢀL.ꢀLiang,ꢀL.ꢀShi,ꢀM.ꢀS.ꢀLiu,ꢀJ.ꢀM.ꢀSun,ꢀDaltonꢀTrans.,ꢀ2014,ꢀ
[46] O.ꢀAkhavan,ꢀCarbon,ꢀ2011,ꢀ49,ꢀ11–18.ꢀ
[47] T.ꢀG.ꢀXu,ꢀL.ꢀW.ꢀZhang,ꢀH.ꢀY.ꢀCheng,ꢀY.ꢀF.ꢀZhu,ꢀAppl.ꢀCatal.ꢀB,ꢀ2011,ꢀ
101,ꢀ382–387.ꢀ
[
43,ꢀ16441–16449.ꢀ
[28] Y.ꢀG.ꢀLin,ꢀY.ꢀK.ꢀHsu,ꢀY.ꢀC.ꢀChen,ꢀL.ꢀC.ꢀChen,ꢀS.ꢀY.ꢀChen,ꢀK.ꢀH.ꢀChen,ꢀ
Nanoscale,ꢀ2012,ꢀ4,ꢀ6515–6519.ꢀ
[48] N.ꢀLi,ꢀG.ꢀLiu,ꢀC.ꢀZhen,ꢀF.ꢀLi,ꢀL.ꢀL.ꢀZhang,ꢀH.ꢀM.ꢀCheng,ꢀAdv.ꢀFunct.ꢀMa‐
ter.,ꢀ2011,ꢀ21,ꢀ1717–1722.ꢀ
[
29] S.ꢀ Cho,ꢀ J.ꢀ W.ꢀ Jang,ꢀ J.ꢀ S.ꢀ Lee,ꢀ K.ꢀ H.ꢀ Lee,ꢀ CrystEngComm,ꢀ 2010,ꢀ 12,ꢀ
[49] J.ꢀP.ꢀLiu,ꢀY.ꢀY.ꢀLi,ꢀR.M.ꢀDing,ꢀJ.ꢀJiang,ꢀY.ꢀY.ꢀHu,ꢀX.ꢀX.ꢀJi,ꢀQ.ꢀB.ꢀChi,ꢀZ.ꢀH.ꢀ
Zhu,ꢀX.ꢀT.ꢀHuang,ꢀJ.ꢀPhys.ꢀChem.ꢀC,ꢀ2009,ꢀ113,ꢀ5336–5339.ꢀ
[50] E.ꢀRokhsat,ꢀO.ꢀAkhavan,ꢀAppl.ꢀSurf.ꢀSci.,ꢀ2016,ꢀ371,ꢀ590–595.ꢀ
[51] J.ꢀ M.ꢀZhang,ꢀ M.ꢀ Vasei,ꢀ Y.ꢀ H.ꢀSang,ꢀ H.ꢀ Liu,ꢀJ.ꢀP.ꢀClaverie,ꢀ ACSꢀ Appl.ꢀ
Mater.ꢀInterfaces,ꢀ2016,ꢀ8,ꢀ1903–1912.ꢀ
3929–3935.ꢀ
[
30] D.ꢀF.ꢀWang,ꢀZ.ꢀG.ꢀZou,ꢀJ.ꢀH.ꢀYe,ꢀChem.ꢀMater.,ꢀ2005,ꢀ17,ꢀ3255–3261.ꢀ
31] D.ꢀJ.ꢀYang,ꢀH.ꢀW.ꢀLiu,ꢀZ.ꢀF.ꢀZheng,ꢀY.ꢀYuan,ꢀJ.ꢀC.ꢀZhao,ꢀE.ꢀR.ꢀWaclawik,ꢀ
X.ꢀB.ꢀKe,ꢀH.ꢀY.ꢀZhu,ꢀJ.ꢀAm.ꢀChem.ꢀSoc.,ꢀ2009,ꢀ131,ꢀ17885–17893.ꢀ
[
[
32] T.ꢀ Wang,ꢀ R.ꢀ Lü,ꢀ P.ꢀ Zhang,ꢀ C.ꢀ J.ꢀ Li,ꢀ J.ꢀ L.ꢀ Gong,ꢀ Nanoscale,ꢀ 2015,ꢀ 7,ꢀ
[52] Y.ꢀHu,ꢀX.ꢀH.ꢀGao,ꢀL.ꢀYu,ꢀY.ꢀR.ꢀWang,ꢀJ.ꢀQ.ꢀNing,ꢀS.ꢀJ.ꢀXu,ꢀX.ꢀW.ꢀLou,ꢀAn‐
gew.ꢀChem.ꢀInt.ꢀEd.,ꢀ2013,ꢀ52,ꢀ5636–5639.ꢀ
77–81.ꢀ
[33] C.ꢀL.ꢀZhang,ꢀM.ꢀF.ꢀShao,ꢀF.ꢀY.ꢀNing,ꢀS.M.ꢀXu,ꢀZ.ꢀH.ꢀLi,ꢀM.ꢀWei,ꢀD.ꢀG.ꢀ
Evans,ꢀX.ꢀDuan,ꢀNanoꢀEnergy,ꢀ2015,ꢀ12,ꢀ231–239.ꢀ
[53] L.ꢀ P.ꢀ Wu,ꢀ Y.ꢀ L.ꢀ Zhang,ꢀ X.ꢀ J.ꢀ Li,ꢀ C.ꢀ P.ꢀ Cen,ꢀ Phys.ꢀChem.ꢀChem.ꢀPhys.,ꢀ
2014,ꢀ16,ꢀ15339–15345.ꢀ
[
34] A.ꢀI.ꢀHochbaum,ꢀP.ꢀD.Yang,ꢀChem.ꢀRev.,ꢀ2010,ꢀ110,ꢀ527546.ꢀ ꢀ
35] G.ꢀM.ꢀWang,ꢀX.ꢀY.ꢀYang,ꢀF.ꢀQian,ꢀJ.ꢀZ.ꢀZhang,ꢀY.ꢀLi,ꢀNanoꢀLett.,ꢀ2010,ꢀ
[54] J.ꢀ L.ꢀ Ouyang,ꢀ M.ꢀ L.ꢀ Chang,ꢀ X.ꢀ J.ꢀ Li,ꢀ J.ꢀ Mater.ꢀ Sci.,ꢀ 2012,ꢀ 47,ꢀ
4187–4193.ꢀ
[
1
0,ꢀ10881092.ꢀ
[55] Y.ꢀ S.ꢀ Liao,ꢀ Z.ꢀ N.ꢀ Hu,ꢀ Q.ꢀ Gu,ꢀ C.ꢀ Xue,ꢀ Molecules,ꢀ 2015,ꢀ 20,ꢀ
18847–18855.
[
36] J.ꢀB.ꢀMu,ꢀC.ꢀL.ꢀShao,ꢀZ.ꢀC.ꢀGuo,ꢀZ.ꢀY.ꢀZhang,ꢀM.ꢀY.ꢀZhang,ꢀP.ꢀZhang,ꢀB.ꢀ
类石墨碳修饰提高ZnO 纳米棒阵列光催化活性和光稳定性的研究
a
a
a
a,b
a,b,c
a,b,*
张学伟 , 张学亮 , 王 鑫 , 刘乐全 , 叶金花
, 王德法
a
天津大学材料科学与工程学院, 天津市材料复合与功能化重点实验室, 先进陶瓷与加工技术教育部重点实验室,
天津大学-NIMS 国际合作实验室, 天津300072, 中国
b
天津化学化工协同创新中心, 天津300072, 中国
c
日本国立物质材料研究机构材料纳米构筑学国际中心(WPI-MANA), 茨城县305-0044, 日本
2
摘要: 半导体光催化是一种理想的太阳能化学转化绿色技术, 可以实现水分解制氢和CO 光还原制备碳氢化合物燃料. 氧
化锌 (ZnO) 作为一种直接带隙半导体材料, 一方面具有性能优异、价格低廉、易制备等优点; 另一方面因光腐蚀而不稳定,
大大限制了该材料的实际应用. 本文提出了一种简单易行的类石墨碳修饰方法, 可以有效提高 ZnO 用于CO
2
光还原的光
催化活性和稳定性.
首先采用水热法在金属锌片基底上生长 ZnO 纳米棒阵列 (ZnO-NRA), 然后通过葡萄糖水热法进行不同含量的类石墨
碳 (C-x) 修饰, 形成 ZnO-NRA/C-x 纳米复合结构, 同步实现碳包覆和碳掺杂. X 射线衍射结果表明, ZnO 纳米棒及
ZnO-NRA/C-x 纳米复合结构都具有良好的纤锌矿型 (Wurtzite) 结构; 而拉曼散射则清楚地证实了类石墨碳的存在. 扫描
电子显微观察显示, 生长的 ZnO 纳米棒长度大约 25 m, 直径为 400700 nm, 沿方向[0001]生长, 端部由六个规则的 (103)
晶面组成, 进一步直观佐证了 ZnO 的典型纤锌矿型结构特征. 透射电子显微分析结果表明, ZnO-NRA/C-x 纳米复合结构
中类石墨碳包覆层厚度大约为 8 nm. ZnO-NRA/C-x 纳米复合结构的 X 射线光电子谱分析结果验证了 CC, CO 和 C=O
键的存在与碳的包覆层相对应; 而 COZn键的出现则是由于碳在 ZnO 中掺杂所引起. 从紫外-可见吸收谱上可观察到
ZnO 的典型吸收带边位置约为 385 nm, 而碳的包覆和掺杂导致 ZnO-NRA/C-x 纳米复合结构的吸收带边发生红移, 并且吸

ꢀ
XueweiꢀZhangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ973–981ꢀ
981ꢀ
收背底明显提高.
电化学阻抗谱测试结果清楚地显示, ZnO-NRA/C-x 纳米复合结构比单纯 ZnO-NRA 的电化学阻抗明显降低, 说明类石
墨碳包覆层大幅度提高了电导性能, 从而有利于光生载流子的分离和传输. 荧光分析结果也表明, 与单纯的 ZnO-NRA 相
比, ZnO-NRA/C-x 纳米复合结构的荧光强度大幅度下降, 进一步证实了 ZnO-NRA/C-x 纳米复合结构比单纯的 ZnO-NRA
更有利于光生载流子的分离和传输. 光电化学测试结果表明, ZnO-NRA/C-x 纳米复合结构的瞬态光电流 4 倍于单纯的
ZnO-NRA, 而 CO
具有稳定的光催化活性和极好的光稳定性.
综上, 我们利用一种简单易行的水热法进行类石墨碳修饰, 成功开发了 ZnO-NRA/C-x 纳米复合结构, 该结构因其优异
的光生电子和空穴的分离和迁移性能, 从而具有显著提升的CO 光还原活性和光稳定性. 本工作证明, 类石墨碳修饰是一
2 2
光还原性能测试也得到一致的结果. 长时间多循环 CO 光还原实验证实, ZnO-NRA/C-x 纳米复合结构
2
种可以广泛借鉴的有效提升半导体材料光催化活性和光稳定性的可行方法.
关键词: 光催化; ZnO 纳米棒阵列; 类石墨碳; 电荷转移; 光稳定性; 二氧化碳 还原
收稿日期: 2017-11-18. 接受日期: 2017-12-28. 出版日期: 2018-05-05.
*
通讯联系人. 电话/传真: (022)27405065; 电子信箱: defawang@tju.edu.cn
基金来源: 国家重点基础研究发展计划(973 计划, 2014CB239300); 国家自然科学基金(51572191, 21633004); 天津市自然科学基
金(13JCYBJC16600).
本文的电子版全文由Elsevier出版社在ScienceDirect上出版(http://www.sciencedirect.com/science/journal/18722067).