Microwave-assisted ionothermal synthesis of hierarchical microcube-like BiOBr with enhanced photocatalytic activity

Article abstract of DOI:10.1016/S1872-2067(18)63080-3

Bismuth oxybromide (BiOBr) with a hierarchical microcube morphology was successfully synthesized via microwave-assisted ionothermal self-assembly method. The as-obtained BiOBr was composed of regular multi-layered nanosheets, which were formed by selective adsorption of ionic liquids on the Br-terminated surface, followed by the formation of hydrogen bond-co-π-π stacking. The synthesized BiOBr exhibited high activity, excellent stability, and superior mineralization ability in the photocatalytic degradation of organic dyes under visible light owing to its enhanced light absorbance and narrow bandgap. Furthermore, photo-generated electrons were determined to be the main active species by comparison with different trapping agents used in the photocatalytic reactions.

Full text of DOI:10.1016/S1872-2067(18)63080-3

ChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1411–1417
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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
Microwave‐assistedꢀionothermalꢀsynthesisꢀofꢀhierarchicalꢀ ꢀ
microcube‐likeꢀBiOBrꢀwithꢀenhancedꢀphotocatalyticꢀactivityꢀ
a,b,
b
b
b,#
YingchunꢀMiaoꢀ *,ꢀZichaoꢀLianꢀ ,ꢀYuningꢀHuoꢀ ,ꢀHexingꢀLiꢀ
ꢀ
aꢀFacultyꢀofꢀChemicalꢀandꢀEnvironmentalꢀScience,ꢀKeyꢀLaboratoryꢀofꢀEnvironmentꢀChemistry,ꢀQujingꢀNormalꢀUniversity,ꢀQujingꢀ655000,ꢀYunnan,ꢀChinaꢀ
bꢀTheꢀEducationꢀMinistryꢀKeyꢀLaboratoryꢀofꢀResourceꢀChemistry,ꢀShanghaiꢀKeyꢀLaboratoryꢀofꢀRareꢀEarthꢀFunctionalꢀMaterials,ꢀShanghaiꢀNormalꢀ ꢀ
University,ꢀShanghaiꢀ200234,ꢀChinaꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
Bismuthꢀoxybromideꢀ(BiOBr)ꢀwithꢀaꢀhierarchicalꢀmicrocubeꢀmorphologyꢀwasꢀsuccessfullyꢀsynthe‐
sizedꢀviaꢀmicrowave‐assistedꢀionothermalꢀself‐assemblyꢀmethod.ꢀTheꢀas‐obtainedꢀBiOBrꢀwasꢀcom‐
posedꢀ ofꢀ regularꢀ multi‐layeredꢀ nanosheets,ꢀ whichꢀ wereꢀ formedꢀ byꢀ selectiveꢀ adsorptionꢀ ofꢀ ionicꢀ
liquidsꢀonꢀtheꢀBr‐terminatedꢀsurface,ꢀfollowedꢀbyꢀtheꢀformationꢀofꢀhydrogenꢀbond‐co‐π‐πꢀstacking.ꢀ
TheꢀsynthesizedꢀBiOBrꢀexhibitedꢀhighꢀactivity,ꢀexcellentꢀstability,ꢀandꢀsuperiorꢀmineralizationꢀabilityꢀ
inꢀ theꢀ photocatalyticꢀ degradationꢀ ofꢀ organicꢀ dyesꢀ underꢀ visibleꢀ lightꢀ owingꢀ toꢀ itsꢀ enhancedꢀ lightꢀ
absorbanceꢀandꢀnarrowꢀbandgap.ꢀFurthermore,ꢀphoto‐generatedꢀelectronsꢀwereꢀdeterminedꢀtoꢀbeꢀ
theꢀ mainꢀ activeꢀ speciesꢀ byꢀ comparisonꢀ withꢀ differentꢀ trappingꢀ agentsꢀ usedꢀ inꢀ theꢀ photocatalyticꢀ
reactions.ꢀ
Receivedꢀ3ꢀMarchꢀ2018ꢀ
Acceptedꢀ25ꢀAprilꢀ2018ꢀ
Publishedꢀ5ꢀAugustꢀ2018ꢀ
Keywords:ꢀ
Microwaveꢀ
BiOBrꢀmicrocubesꢀ
Self‐assemblyꢀ
Photocatalyticꢀdegradationꢀ
Mineralizationꢀability
©ꢀ2018,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
1
.ꢀ ꢀ Introductionꢀ
organicꢀ positiveꢀ ionsꢀ withꢀ aꢀ highꢀ polarizabilityꢀ [5].ꢀ Toꢀ date,ꢀ
variousꢀfunctionalꢀmaterialsꢀhaveꢀbeenꢀsynthesizedꢀbyꢀtheꢀmi‐
crowave‐assistedꢀ ionothermalꢀ method,ꢀ includingꢀ nanorods,ꢀ
nanowires,ꢀandꢀhollowꢀmicrospheresꢀ[6–13].ꢀ
Asꢀisꢀwellꢀknown,ꢀphotocatalysisꢀisꢀaꢀpowerfulꢀstrategyꢀforꢀ
environmentalꢀ cleaningꢀ viaꢀ decompositionꢀ ofꢀ organicꢀ pollu‐
Recently,ꢀ microwave‐assistedꢀ ionothermalꢀ synthesisꢀ hasꢀ
receivedꢀconsiderableꢀ attentionꢀowingꢀtoꢀitsꢀ rapidꢀvolumetricꢀ
heating,ꢀ highꢀ reactionꢀ rate,ꢀ shortꢀ reactionꢀ time,ꢀ enhancedꢀ
productꢀ selectivity,ꢀ environmentalꢀ friendliness,ꢀ andꢀ energyꢀ
efficiencyꢀ comparedꢀ toꢀ conventionalꢀ heatingꢀ routesꢀ [1,2].ꢀ
Meanwhile,ꢀionicꢀliquidsꢀ(ILs)ꢀhaveꢀbeenꢀfoundꢀtoꢀdisplayꢀhighꢀ
fluidity,ꢀ lowꢀ meltingꢀ temperature,ꢀ extendedꢀ liquid‐stateꢀ tem‐
peratureꢀ ranges,ꢀ highꢀ ionicꢀ conductivity,ꢀ abilityꢀ toꢀ dissolveꢀ inꢀ
variousꢀmaterials,ꢀandꢀabsentꢀmeasurableꢀvaporꢀpressureꢀ[3,4].ꢀ
Inꢀ particular,ꢀ ILsꢀ areꢀ goodꢀ mediaꢀ forꢀ microwaveꢀ absorption,ꢀ
leadingꢀtoꢀaꢀhighꢀheatingꢀrateꢀbecauseꢀofꢀtheꢀpresenceꢀofꢀmanyꢀ
tantsꢀorꢀforꢀH
ꢀproductionꢀbyꢀwaterꢀsplittingꢀ[14,15].ꢀBismuthꢀ
2
oxybromideꢀ(BiOBr)ꢀhasꢀreceivedꢀconsiderableꢀattentionꢀdueꢀtoꢀ
itsꢀ narrowꢀ energyꢀ bandgapꢀ forꢀ absorbingꢀ visibleꢀ light,ꢀ lowꢀ
photo‐inducedꢀ electron‐holeꢀ recombination,ꢀ nontoxicity,ꢀ andꢀ
strongꢀoxidizingꢀpowerꢀ[16–22].ꢀAlthoughꢀvariousꢀBiOBrꢀpho‐
tocatalystsꢀhaveꢀbeenꢀsynthesizedꢀbyꢀtraditionalꢀsolvothermalꢀ
ꢀ
methodsꢀ[23–27],theꢀdevelopmentꢀofꢀnew,ꢀgreen,ꢀandꢀefficientꢀ
*
ꢀ
ꢀCorrespondingꢀauthor.ꢀE‐mail:ꢀmiaoyingchun1979@sohu.comꢀ
Correspondingꢀauthor.ꢀE‐mail:ꢀhexing‐li@shnu.edu.cnꢀ
#
Thisꢀ workꢀ wasꢀ supportedꢀ byꢀ theꢀ Nationalꢀ Naturalꢀ Scienceꢀ Foundationꢀ ofꢀ Chinaꢀ (20937003,ꢀ 21261140333,ꢀ 21237003,ꢀ 21207091,ꢀ 21577092,ꢀ
171101231),ꢀShanghaiꢀGovernmentꢀ(12230706000,ꢀ11JC1409000,ꢀ12YZ091,ꢀ15520711300),ꢀYunnanꢀAppliedꢀBasicꢀResearchꢀProjectꢀofꢀProvinceꢀ
2013FZ109,ꢀ2016FB016),ꢀandꢀKeyꢀProjectsꢀofꢀYunnanꢀProvincialꢀDepartmentꢀofꢀEducationꢀ(2015Z183,ꢀ2016ZZX207).ꢀ ꢀ
DOI:ꢀ10.1016/S1872‐2067(18)63080‐3ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ39,ꢀNo.ꢀ8,ꢀAugustꢀ2018ꢀ ꢀ ꢀ
2
(

1412ꢀ
YingchunꢀMiaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1411–1417ꢀ
synthesisꢀmethodsꢀtoꢀachieveꢀaꢀnovelꢀstructureꢀisꢀstillꢀrequired.ꢀ
Herein,ꢀweꢀreportedꢀforꢀtheꢀfirstꢀtimeꢀtheꢀsynthesisꢀofꢀhier‐
archicalꢀBiOBrꢀmicrocubesꢀbyꢀmicrowave‐assistedꢀionothermalꢀ
self‐assemblyꢀmethod.ꢀThisꢀmethodꢀrequiredꢀaꢀshortꢀreactionꢀ
timeꢀandꢀcouldꢀachieveꢀtheꢀdesiredꢀmorphologyꢀandꢀstructure.ꢀ
Moreover,ꢀ theꢀ as‐preparedꢀ BiOBrꢀ exhibitedꢀ highꢀ activityꢀ andꢀ
excellentꢀstabilityꢀinꢀphotocatalyticꢀdegradationꢀofꢀorganicꢀdyesꢀ
underꢀvisibleꢀlightꢀowingꢀtoꢀitsꢀ strongꢀlightꢀharvestingꢀ abilityꢀ
andꢀuniqueꢀstructure.ꢀ ꢀ
spectraꢀ (UV‐Visꢀ DRS,ꢀ Varianꢀ Caryꢀ 500).ꢀ Theꢀ surfaceꢀ photo‐
voltageꢀspectraꢀ(SPS)ꢀwereꢀmeasuredꢀonꢀaꢀself‐designedꢀsystemꢀ
consistingꢀofꢀaꢀ500ꢀWꢀxenonꢀlampꢀ (CHFꢀXM500W,ꢀ Stusttech)ꢀ
combinedꢀ withꢀ aꢀ double‐prismꢀ monochromatorꢀ (Omini‐500,ꢀ
Zolix)ꢀ asꢀ theꢀ lightꢀ source,ꢀ aꢀ lightꢀ chopperꢀ (~23ꢀ Hz,ꢀ SR540,ꢀ
Stanford),ꢀandꢀaꢀlock‐inꢀamplifierꢀ(SR830‐DSP,ꢀStanford).ꢀTheꢀ
photovoltaicꢀcellꢀhadꢀaꢀsandwichꢀstructureꢀofꢀITO‐sample‐ITO.ꢀ ꢀ
2.3.ꢀ ꢀ Photocatalyticꢀactivityꢀtestꢀ
2
.ꢀ ꢀ Experimentalꢀ
Photocatalyticꢀ degradationꢀ wasꢀ carriedꢀ outꢀ atꢀ 30ꢀ °Cꢀ inꢀ aꢀ
self‐designedꢀ 250ꢀ mLꢀ reactorꢀ containingꢀ 0.025ꢀ gꢀ catalystꢀ andꢀ
10.0ꢀmg/Lꢀorganicꢀdyeꢀinꢀaꢀ100ꢀmLꢀaqueousꢀsolution.ꢀAꢀ300ꢀWꢀ
Xeꢀlampꢀwasꢀusedꢀasꢀtheꢀlightꢀsource,ꢀ andꢀlightꢀwithꢀaꢀwave‐
lengthꢀ shorterꢀ thanꢀ 420ꢀ nmꢀ wasꢀ cut‐offꢀ usingꢀ aꢀ glassꢀ filterꢀ
(JB‐420ꢀ nm).ꢀ Duringꢀ theꢀ reactionꢀ process,ꢀ theꢀ mixtureꢀ wasꢀ
sampledꢀatꢀspecifiedꢀtimeꢀintervalsꢀforꢀmeasuringꢀtheꢀconcen‐
trationꢀofꢀtheꢀunreactedꢀdyeꢀusingꢀaꢀUV‐visꢀspectrophotometerꢀ
(UV‐7504PC)ꢀatꢀtheꢀcharacteristicꢀwavelength.ꢀTheꢀtotalꢀorgan‐
icꢀcarbonꢀ(TOC)ꢀwasꢀdeterminedꢀonꢀaꢀVarioꢀTOCꢀanalyzer.ꢀTheꢀ
reproducibilityꢀ ofꢀ theꢀ resultsꢀ wasꢀ checkedꢀ byꢀ repeatingꢀ theꢀ
experimentsꢀatꢀ leastꢀthreeꢀtimesꢀ andꢀwasꢀ foundꢀtoꢀ beꢀwithinꢀ
acceptableꢀlimitsꢀ(±6%).ꢀ
2.1.ꢀ ꢀ Sampleꢀpreparationꢀ
Inꢀbrief,ꢀ1.68ꢀgꢀBi(NO
3 3
)
·5H Oꢀandꢀtheꢀrequiredꢀamountꢀofꢀ
2
1‐hexadecyl‐3‐methylimidazolium‐bromideꢀ (HB)ꢀ wereꢀ dis‐
solvedꢀ inꢀ 30ꢀ mLꢀ ofꢀ ethyleneꢀ glycolꢀ (EG)ꢀ andꢀ magneticallyꢀ
stirredꢀforꢀ30ꢀminꢀtoꢀformꢀaꢀhomogenousꢀsolution.ꢀTheꢀmolarꢀ
ratioꢀofꢀBiꢀtoꢀBrꢀwasꢀcontrolledꢀtoꢀbeꢀ0.4,ꢀ0.8,ꢀandꢀ1.1ꢀinꢀthreeꢀ
parallelꢀexperiments.ꢀTheꢀsolutionꢀwasꢀthenꢀtransferredꢀintoꢀaꢀ
50ꢀ mLꢀ teflon‐linedꢀ autoclaveꢀ andꢀ heatedꢀ toꢀ 160ꢀ °Cꢀ byꢀ micro‐
wavesꢀ(2.45ꢀGHz,ꢀ1000ꢀW).ꢀAfterꢀaꢀdesiredꢀreactionꢀtime,ꢀtheꢀ
mixtureꢀ wasꢀ cooledꢀ toꢀ roomꢀ temperature.ꢀ Theꢀ productꢀ wasꢀ
separatedꢀbyꢀfiltering,ꢀwashedꢀwithꢀethanol,ꢀdriedꢀatꢀ80ꢀ°Cꢀinꢀairꢀ
overnight.ꢀTheꢀfinalꢀparticlesꢀwereꢀthenꢀannealedꢀatꢀ400ꢀ°Cꢀforꢀ
3.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
4ꢀhꢀinꢀairꢀtoꢀpromoteꢀcrystallization.ꢀTheꢀas‐synthesizedꢀBiOBrꢀ
wasꢀdenotedꢀasꢀBiOBr.ꢀ
3.1.ꢀ ꢀ Structuralꢀcharacterizationꢀofꢀmicrocube‐likeꢀBiOBrꢀ
Forꢀ comparison,ꢀ BiOBrꢀ wasꢀ alsoꢀ synthesizedꢀ usingꢀ
1‐octyl‐3‐methylimidazolium‐bromideꢀ
(OB),ꢀ
3.1.1.ꢀ ꢀ FESEM,ꢀTEM,ꢀXRD,ꢀandꢀXPSꢀresultsꢀ
1
‐hexyl‐3‐methylimidazolium‐bromideꢀ (hb),ꢀ aꢀ mixtureꢀ ofꢀ KBrꢀ
TheꢀFESEMꢀimagesꢀofꢀBiOBrꢀ(Fig.ꢀ1(a)(c))ꢀshowedꢀuniformꢀ
microcubesꢀofꢀ4ꢀμmꢀassembledꢀbyꢀnanosheetsꢀwithꢀthicknessesꢀ
lessꢀ thanꢀ 50ꢀ nm.ꢀ Theꢀ TEMꢀ imageꢀ (Fig.ꢀ 1(d))ꢀ showedꢀ aꢀ solidꢀ
andꢀ1‐hexadecyl‐3‐methylimidazoliumꢀnitrateꢀ(HK),ꢀaꢀmixtureꢀ
ofꢀKClꢀandꢀHK,ꢀcetrimoniumꢀbromideꢀ(CTAB),ꢀandꢀaꢀmixtureꢀofꢀ
1‐methyl‐imidazoliumꢀ(MI)ꢀandꢀKBrꢀinsteadꢀofꢀHB,ꢀwhichꢀwereꢀ
denotedꢀ asꢀ BiOBrꢀ (OB),ꢀ BiOBrꢀ (hb),ꢀ BiOBrꢀ (HK),ꢀ BiOClꢀ (HK),ꢀ
BiOBrꢀ (CTAB),ꢀ andꢀ BiOBrꢀ (MI),ꢀ respectively.ꢀ Crushedꢀ BiOBrꢀ
wasꢀ synthesizedꢀ byꢀ grindingꢀ 0.2ꢀ gꢀ ofꢀ theꢀ BiOBrꢀ sampleꢀ andꢀ
ethanolꢀforꢀ120ꢀminꢀusingꢀaꢀpestleꢀandꢀmortar.ꢀ
2.2.ꢀ ꢀ Characterizationꢀ
TheꢀcrystalꢀstructureꢀwasꢀinvestigatedꢀbyꢀX‐rayꢀdiffractionꢀ
(
XRD,ꢀRigakuꢀD/Max‐2000)ꢀandꢀtheꢀfineꢀstructureꢀwasꢀanalyzedꢀ
byꢀ Fourierꢀ transformꢀ infraredꢀ (FTIR)ꢀ spectroscopyꢀ (NEXUSꢀ
70).ꢀ Theꢀ surfaceꢀ morphologyꢀ wasꢀ observedꢀ byꢀ transmissionꢀ
4
electronicꢀ microscopyꢀ (TEM,ꢀ JEM‐2010)ꢀ andꢀ fieldꢀ emissionꢀ
scanningꢀ electronꢀ microscopyꢀ (FESEM,ꢀ HITACHIꢀ S‐4800);ꢀ theꢀ
compositionalꢀ dataꢀ ofꢀ theꢀ samplesꢀ wereꢀ alsoꢀ recordedꢀ usingꢀ
energyꢀdispersiveꢀX‐rayꢀspectroscopyꢀ(EDX).ꢀTheꢀthermalꢀsta‐
bilityꢀwasꢀinvestigatedꢀbyꢀaꢀthermogravimetricꢀanalysisꢀ(TGA,ꢀ
DTG‐60H).ꢀX‐rayꢀphotoelectronꢀspectroscopyꢀ(XPS,ꢀVersaꢀProbeꢀ
PHIꢀ 5000)ꢀ wasꢀ employedꢀ toꢀ determineꢀ theꢀ surfaceꢀ electronicꢀ
states.ꢀAllꢀtheꢀbindingꢀenergyꢀvaluesꢀwereꢀcalibratedꢀusingꢀCꢀ1sꢀ
(284.8ꢀ eV)ꢀ asꢀ reference.ꢀ N
2
ꢀ adsorption‐desorptionꢀ isothermsꢀ
wereꢀmeasuredꢀonꢀaꢀTriStarꢀIIꢀ3020ꢀatꢀ–196ꢀ°Cꢀandꢀtheꢀsurfaceꢀ
areaꢀ wasꢀ calculatedꢀ byꢀ applyingꢀ theꢀ Brunauer‐Emmett‐Tellerꢀ
Fig.ꢀ 1.ꢀ FESEMꢀ (a–c),ꢀ TEMꢀ (d),ꢀ HRTEMꢀ imagesꢀ (e)ꢀ (insetꢀ isꢀ theꢀ SAEDꢀ
image),ꢀandꢀXRDꢀpatternsꢀ(f)ꢀofꢀas‐preparedꢀBiOBr.ꢀ
(BET)ꢀmodelꢀonꢀtheꢀdesorptionꢀbranches.ꢀTheꢀopticalꢀproper‐
tiesꢀwereꢀdeterminedꢀ byꢀultraviolet‐visibleꢀ diffuseꢀreflectanceꢀ

ꢀ
YingchunꢀMiaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1411–1417ꢀ
1413ꢀ
microcube.ꢀMeanwhile,ꢀtheꢀhigh‐resolutionꢀTEMꢀ(HRTEM)ꢀim‐
ageꢀ (Fig.ꢀ 1(e))ꢀ demonstratedꢀ well‐crystallizedꢀ BiOBrꢀ meso‐
crystalsꢀcorrespondingꢀtoꢀtheꢀ(110)ꢀplaneꢀwithꢀaꢀlatticeꢀspacingꢀ
ofꢀ0.277ꢀnmꢀ[27],ꢀwhichꢀcouldꢀbeꢀfurtherꢀconfirmedꢀbyꢀtheꢀse‐
lectedꢀareaꢀelectronꢀdiffractionꢀ(SAED)ꢀpatternsꢀwithꢀscatteredꢀ
brightꢀ spotsꢀ representingꢀ theꢀ (110)ꢀ andꢀ (100)ꢀ latticeꢀ planes,ꢀ
indicatingꢀ tetragonalꢀ BiOBrꢀ mesocrystalsꢀ (insetꢀ ofꢀ Fig.ꢀ 1(e)).ꢀ
Furthermore,ꢀtheꢀXRDꢀresultꢀ(Fig.ꢀ1(f))ꢀdemonstratedꢀthatꢀtheꢀ
as‐obtainedꢀ BiOBrꢀ hadꢀ aꢀ highlyꢀ crystallineꢀ pureꢀ tetragonalꢀ
phaseꢀ(JCPDSꢀNo.ꢀ73‐2061).ꢀInꢀaddition,ꢀtheꢀEDXꢀspectrumꢀ(Fig.ꢀ
S1)ꢀdeterminedꢀtheꢀBi/Br/Oꢀmolarꢀratioꢀtoꢀbeꢀ1.00:1.00:1.00ꢀinꢀ
BiOBr,ꢀcorrespondingꢀtoꢀtheꢀpureꢀstoichiometricꢀratioꢀofꢀBiOBr.ꢀ
TheꢀXPSꢀresultsꢀ(Fig.ꢀS2)ꢀalsoꢀconfirmedꢀtheꢀpureꢀBiOBrꢀphaseꢀ
withꢀaꢀBi:O:Brꢀmolarꢀratioꢀofꢀ1.26:1.07:1.00ꢀandꢀBiꢀ4f,ꢀOꢀ1s,ꢀandꢀ
Brꢀ 3dꢀ bindingꢀ energiesꢀ ofꢀ 164.7/159.4ꢀ [28],ꢀ 530.2ꢀ [29],ꢀ andꢀ
Bi
O
Br
Fig.ꢀ 3.ꢀ Schemeꢀ ofꢀ formationꢀ ofꢀ hierarchicalꢀ BiOBrꢀ microcubesꢀ underꢀ
microwave‐assistedꢀionothermalꢀconditions.ꢀ
68.6ꢀeVꢀ[30],ꢀrespectively.ꢀ
Asꢀ shownꢀ inꢀ Fig.ꢀ 2,ꢀ onlyꢀ nanoparticlesꢀ withꢀ aꢀ diameterꢀ ofꢀ
strongꢀmicrowaveꢀabsorbanceꢀcausedꢀbyꢀtheꢀhighꢀionicꢀconduc‐
tivityꢀandꢀpolarizabilityꢀofꢀHB.ꢀ ꢀ
aroundꢀ100ꢀnmꢀwereꢀobtainedꢀinꢀtheꢀearlyꢀstage.ꢀAfterꢀmicro‐
wave‐assistedꢀILꢀtreatmentꢀforꢀ1ꢀmin,ꢀtheseꢀnanoparticlesꢀgrewꢀ
intoꢀseparatedꢀnanosheetsꢀwithꢀaꢀthicknessꢀofꢀaroundꢀ20ꢀnm,ꢀ
whichꢀ couldꢀ beꢀ attributedꢀ toꢀ theꢀ selectiveꢀ adsorptionꢀ ofꢀ HBꢀ
cationsꢀ onꢀ differentꢀ facetsꢀ ofꢀ BiOBr,ꢀ leadingꢀ toꢀ priori‐
ty‐orientatedꢀtwo‐dimensionalꢀ(2D)ꢀcrystalꢀgrowth.ꢀWhenꢀtheꢀ
reactionꢀ timeꢀ wasꢀ increasedꢀ toꢀ 30ꢀ min,ꢀ theseꢀ nanosheetsꢀ as‐
sembledꢀontoꢀtheꢀoriginalꢀnanoparticlesꢀowingꢀtoꢀtheꢀhighꢀsur‐
faceꢀenergyꢀandꢀsurfaceꢀtemperatureꢀresultingꢀfromꢀtheꢀstrongꢀ
adsorptionꢀ ofꢀ theꢀ microwave,ꢀ formingꢀ flower‐likeꢀ micro‐
spheres.ꢀFurthermore,ꢀatꢀ40ꢀminꢀmicrocubesꢀwereꢀassembledꢀ
byꢀtheꢀlayer‐by‐layerꢀmechanismꢀdueꢀtoꢀtheꢀgrowthꢀofꢀtheꢀcoreꢀ
nanoparticlesꢀ intoꢀ nanosheets.ꢀ Moreover,ꢀ withꢀ increasingꢀ
quantityꢀofꢀHB,ꢀtheꢀas‐preparedꢀsamplesꢀtransitionedꢀfromꢀmi‐
crosphericalꢀ BiOBrꢀ superstructuresꢀ toꢀ flower‐likeꢀ structuresꢀ
andꢀ thenꢀ microcube‐likeꢀ BiOBrꢀ withꢀ regularꢀ nanosheetsꢀ (Fig.ꢀ
S3).ꢀFurthermore,ꢀtheꢀXRDꢀpatternsꢀ(Fig.ꢀ2(g))ꢀsuggestedꢀthatꢀ
theꢀmicrowave‐assistedꢀILꢀmethodꢀenabledꢀtheꢀreactionꢀtoꢀbeꢀ
completedꢀwithinꢀaꢀveryꢀshortꢀtimeꢀ[31–36],ꢀpossiblyꢀdueꢀtoꢀtheꢀ
3.1.2.ꢀ ꢀ FormationꢀofꢀBiOBrꢀ
Fig.ꢀ3ꢀbrieflyꢀillustratesꢀtheꢀformationꢀofꢀhierarchicalꢀBiOBrꢀ
microcubesꢀ byꢀ microwave‐assistedꢀ ionothermalꢀ self‐assemblyꢀ
]2+ꢀcouldꢀbeꢀformedꢀviaꢀ
basedꢀonꢀtheꢀaboveꢀanalysis.ꢀTheꢀ[Bi
2 2
O
reactionꢀ(1)ꢀandꢀ(2)ꢀ[29],ꢀfollowedꢀbyꢀtheꢀformationꢀofꢀBiOBrꢀ
nucleiꢀbyꢀreactionꢀ(3)ꢀandꢀ(4).ꢀ ꢀ
OHCH CH OH
2
CH CHO+H O
3 2
2
ꢀ
ꢀ ꢀ ꢀ (1)ꢀ
3+
2+
+
6
Bi ꢀ +ꢀ 6H
2
Oꢀ ꢀ 3[Bi
2
O
2
] ꢀ +ꢀ 12H ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ (2)ꢀ
‒ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ ꢀ
ꢀ
ꢀ
ꢀ +ꢀ Br
ꢀ ꢀ
(3)ꢀ
(4)ꢀ
−
2+
ꢀ
[Bi O
2 2
] ꢀ+ꢀ2Br ꢀ2BiOBrꢀ ꢀ ꢀ
ꢀ
ꢀ
Theꢀnanoparticlesꢀmightꢀstackꢀthroughꢀtheꢀselectiveꢀadsorp‐
tionꢀofꢀHBꢀasꢀtheꢀcappingꢀagentꢀandꢀmassꢀdiffusion.ꢀTheꢀsuperi‐
orꢀ advantageꢀ ofꢀ theꢀ ILsꢀ couldꢀ leadꢀ toꢀ hydrogenꢀ bond‐co‐ꢀ
stackingꢀinꢀtheꢀliquidꢀstateꢀ[37].ꢀTheꢀcationsꢀofꢀtheꢀILsꢀcouldꢀbeꢀ
(
a)
(b)
(c)
(g)
40 min
3
0 min
0 min
2
(d)
(e)
(f)
10 min
5
min
min
1
10
20
30
40
50
60

2
 
Fig.ꢀ2.ꢀFESEMꢀimagesꢀ((a)–(f))ꢀandꢀXRDꢀpatternsꢀ(g)ꢀofꢀformationꢀofꢀBiOBrꢀmesocrystalsꢀatꢀdifferentꢀreactionꢀtimes.ꢀ(a)ꢀ0ꢀmin;ꢀ(b)ꢀ1ꢀmin;ꢀ(c)ꢀ5ꢀmin;ꢀ(d)ꢀ
0ꢀmin;ꢀ(e)ꢀ30ꢀmin;ꢀandꢀ(f)ꢀ40ꢀmin.ꢀScaleꢀbar:ꢀ1ꢀμm.ꢀ
2

1414ꢀ
YingchunꢀMiaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1411–1417ꢀ
‒
1
easilyꢀadsorbedꢀonꢀtheꢀBr‐terminatedꢀsurfaceꢀbyꢀelectrostaticꢀ
forces,ꢀandꢀtheꢀhydrogenꢀbondꢀformedꢀbetweenꢀtheꢀhydrogenꢀ
atomꢀatꢀtheꢀC2ꢀpositionꢀofꢀtheꢀimidazoleꢀringꢀandꢀtheꢀbromineꢀ
sorptionꢀ bandꢀ atꢀ 3077ꢀ cm ,ꢀ correspondingꢀ toꢀ theꢀ stretchingꢀ
vibrationꢀofꢀC2‐Hꢀinꢀtheꢀimidazoleꢀring.ꢀMeanwhile,ꢀtheꢀpeaksꢀatꢀ
‒
1
1575,ꢀ 1468,ꢀ andꢀ 1174ꢀ cm ꢀ wereꢀ attributedꢀ toꢀ theꢀ skeletonꢀ
stretchingꢀ vibrationꢀ signalꢀ ofꢀ theꢀ imidazoleꢀ ringꢀ andꢀ becameꢀ
broaderꢀandꢀweakerꢀinꢀtheꢀFTIRꢀspectraꢀofꢀBiOBrꢀ[37].ꢀTheseꢀ
resultsꢀindicatedꢀthatꢀthereꢀwereꢀstrongꢀinteractionsꢀbetweenꢀ
theꢀILsꢀ andꢀBiOBr,ꢀconfirmingꢀtheꢀ existenceꢀofꢀ theꢀ strongꢀhy‐
drogenꢀ bondsꢀ inꢀ C2(HB)‐H‐Br(BiOBr),ꢀ whichꢀ wasꢀ similarꢀ toꢀ
−
atomꢀofꢀBr ꢀ[BiOBr]ꢀcouldꢀactꢀasꢀanꢀeffectiveꢀbridgeꢀtoꢀconnectꢀ
theꢀ Br‐terminatedꢀ planeꢀ ofꢀ theꢀ producedꢀ metal‐oxideꢀ nucleiꢀ
andꢀtheꢀcationsꢀofꢀtheꢀILs.ꢀAlso,ꢀtheꢀILꢀcationsꢀwouldꢀbeꢀalignedꢀ
byꢀadditionalꢀꢀinteractionsꢀamongꢀtheꢀimidazoliumꢀringsꢀofꢀ
HBꢀtoꢀfacilitateꢀtheꢀproposedꢀrelocationꢀofꢀmoleculesꢀbasedꢀonꢀ
HB’sꢀabilityꢀtoꢀself‐assembleꢀintoꢀstabilizedꢀorderedꢀstructures.ꢀ
Theꢀhydrogenꢀbond‐co‐ꢀstackingꢀcouldꢀdecreaseꢀtheꢀpolari‐
tyꢀofꢀtheꢀselectiveꢀadsorptionꢀsurfaceꢀandꢀthusꢀrestrainꢀitsꢀmi‐
crowaveꢀabsorptionꢀability,ꢀretardingꢀtheꢀcrystalꢀgrowthꢀofꢀtheꢀ
−1
previousꢀ resultsꢀ [37,42].ꢀ Moreover,ꢀ theꢀ peakꢀ atꢀ 1038ꢀ cm ,ꢀ
characteristicꢀofꢀtheꢀC–Nꢀstretchingꢀvibrationꢀ(νC–N)ꢀmodeꢀinꢀtheꢀ
imidazoleꢀringꢀofꢀBiOBrꢀwithoutꢀcalcination,ꢀbecameꢀnarrowerꢀ
andꢀstrongerꢀthanꢀthatꢀobservedꢀinꢀtheꢀspectraꢀforꢀHBꢀandꢀBi‐
OBrꢀ+ꢀHBꢀ+ꢀEG.ꢀThisꢀcouldꢀbeꢀascribedꢀtoꢀtheꢀstrongerꢀinterac‐
tionꢀbetweenꢀtheꢀaromaticꢀringsꢀandꢀtheꢀBiOBrꢀsurfaceꢀ[37],ꢀasꢀ
confirmedꢀ byꢀ theꢀ aforementionedꢀ SPSꢀ spectra.ꢀ Theseꢀ resultsꢀ
stronglyꢀ supportedꢀ thatꢀ theꢀ hydrogenꢀ bond‐co‐π‐πꢀ stackingꢀ
wasꢀresponsibleꢀforꢀtheꢀformationꢀofꢀBiOBrꢀmicrocubes.ꢀ ꢀ
2Dꢀselectiveꢀadsorptionꢀsurfaceꢀtoꢀformꢀaꢀ3Dꢀcubicꢀarchitecture.ꢀ
Theꢀꢀstackingꢀcouldꢀresultꢀinꢀstrongꢀcloudꢀdensityꢀandꢀstaticꢀ
repulsionꢀinꢀeachꢀnanosheetꢀbecauseꢀtheꢀzetaꢀpotentialsꢀofꢀBi‐
OBrꢀwithoutꢀcalcination,ꢀBiOBr,ꢀandꢀtheꢀmixtureꢀofꢀBiOBrꢀ+ꢀEGꢀ
+ꢀHBꢀwereꢀ −10.5,ꢀ−0.448,ꢀandꢀ −0.345ꢀmVꢀrespectively,ꢀ whichꢀ
couldꢀadjustꢀtheꢀintervalsꢀofꢀtheꢀnanosheetꢀandꢀtheꢀthicknessesꢀ
ofꢀtheꢀmicrocubes.ꢀ ꢀ
Severalꢀadditionalꢀexperimentsꢀwereꢀconductedꢀtoꢀconfirmꢀ
theꢀaboveꢀhypothesis.ꢀCTABꢀcouldꢀnotꢀeffectivelyꢀachieveꢀselec‐
tiveꢀ adsorptionꢀ andꢀ hydrogenꢀ bond‐co‐π‐stacking.ꢀ Whenꢀ itꢀ
wasꢀ usedꢀ insteadꢀ ofꢀ HB,ꢀ onlyꢀ flower‐likeꢀ microspheresꢀ (Fig.ꢀ
S7(a)ꢀandꢀ(b))ꢀofꢀBiOBrꢀwereꢀachievedꢀdueꢀtoꢀtheꢀlayer‐by‐layerꢀ
structureꢀ[43].ꢀWhenꢀ1:1ꢀmoleꢀratioꢀofꢀOBꢀorꢀhbꢀwasꢀusedꢀin‐
steadꢀofꢀHB,ꢀBiOBrꢀformedꢀwell‐organizedꢀstackedꢀmicrocubesꢀ
(Fig.ꢀ S7(c)ꢀ andꢀ (f)).ꢀ Interestingly,ꢀ theꢀ shorterꢀ theꢀ branchedꢀ
(carbon)ꢀchainꢀonꢀtheꢀN1ꢀ(IL),ꢀtheꢀweakerꢀwasꢀtheꢀstereospe‐
cificꢀ blockade.ꢀ Whenꢀ aꢀ mixtureꢀ ofꢀ HKꢀ andꢀ KBrꢀ replacedꢀ HB,ꢀ
BiOBrꢀmicrocubesꢀwereꢀobtainedꢀ(Fig.ꢀS8(a)ꢀandꢀ(b)).ꢀSimilarly,ꢀ
whenꢀaꢀmixtureꢀofꢀHKꢀandꢀKClꢀreplacedꢀHB,ꢀBiOClꢀmicrocubesꢀ
wereꢀachievedꢀ(Fig.ꢀS8(c)ꢀandꢀ(d)).ꢀMoreꢀinterestingly,ꢀwhenꢀaꢀ
mixtureꢀofꢀMIꢀandꢀKBrꢀwasꢀusedꢀinsteadꢀofꢀHB,ꢀBiOBrꢀmicro‐
cubesꢀwasꢀobtainedꢀevenꢀinꢀtheꢀabsenceꢀofꢀanꢀILꢀ(Fig.ꢀS8(e)ꢀandꢀ
(f)).ꢀTheseꢀresultsꢀfurtherꢀconfirmedꢀtheꢀkeyꢀroleꢀofꢀtheꢀhydro‐
genꢀbond‐co‐π‐πꢀstackingꢀinꢀBiOBrꢀformation.ꢀ
TheꢀTGAꢀcurveꢀ(Fig.ꢀS4)ꢀrevealedꢀaꢀhighꢀorganicꢀcontentꢀ(ca.ꢀ
12.7%ꢀbyꢀweight)ꢀinꢀBiOBrꢀwithoutꢀcalcination.ꢀTheꢀDRSꢀspec‐
traꢀ inꢀ Fig.ꢀ 4(a)ꢀ revealedꢀ thatꢀ BiOBrꢀ displayedꢀ aꢀ muchꢀ higherꢀ
lightꢀabsorbanceꢀthanꢀcrushedꢀBiOBrꢀ(Fig.ꢀS5),ꢀwhichꢀcouldꢀbeꢀ
attributedꢀ toꢀ theꢀ multipleꢀ lightꢀ reflectionsꢀ betweenꢀ theꢀ
nanosheetsꢀinꢀtheꢀmicrocubes.ꢀTheꢀbandgapꢀobviouslyꢀwidenedꢀ
fromꢀ2.56ꢀtoꢀ2.66ꢀeVꢀafterꢀcrushingꢀ(insetꢀofꢀFig.ꢀ4(a)).ꢀTheꢀSPSꢀ
spectraꢀ (Fig.ꢀ 4(b))ꢀ confirmedꢀ thatꢀ BiOBrꢀ withoutꢀ calcinationꢀ
displayedꢀseveralꢀpeaksꢀdueꢀtoꢀtheꢀpresenceꢀofꢀvariousꢀorganicꢀ
species.ꢀAfterꢀcalcination,ꢀonlyꢀtwoꢀphotovoltaicꢀpeaks,ꢀcorre‐
spondingꢀ toꢀ twoꢀ discreteꢀ valenceꢀ bandsꢀ inꢀ BiOBr,ꢀ wereꢀ ob‐
servedꢀdueꢀtoꢀtheꢀpresenceꢀofꢀOꢀ2PꢀandꢀBrꢀ4Pꢀorbitalsꢀ(insetꢀofꢀ
Fig.ꢀ4(b))ꢀ[38‒40].ꢀThisꢀcouldꢀalsoꢀaccountꢀforꢀtheꢀspectralꢀre‐
sponsesꢀinꢀbothꢀUVꢀandꢀvisibleꢀregions,ꢀwhichꢀcorrespondedꢀtoꢀ
anꢀindirectꢀbandgapꢀofꢀ2.56ꢀeVꢀinꢀBiOBrꢀ(Fig.ꢀ4(a))ꢀ[41].ꢀMore‐
over,ꢀtheꢀphotovoltaicꢀresponsesꢀofꢀmixedꢀBiOBr,ꢀEG,ꢀandꢀHBꢀ
wereꢀweakerꢀthanꢀthoseꢀofꢀBiOBrꢀowingꢀtoꢀtheꢀabsenceꢀofꢀtheꢀ
hydrogenꢀbond‐co‐ꢀstackingꢀbecauseꢀBiOBrꢀwasꢀcoveredꢀbyꢀ
EGꢀandꢀHB,ꢀleadingꢀtoꢀlimitedꢀlightꢀabsorption.ꢀTheꢀFTIRꢀspec‐
traꢀ(Fig.ꢀS6)ꢀdisplayedꢀsignificantlyꢀdifferentꢀstructuresꢀforꢀpureꢀ
HBꢀ andꢀ BiOBrꢀ withoutꢀ calcination.ꢀ Weꢀ couldꢀ observeꢀ anꢀ ab‐
3.2.ꢀ ꢀ Photocatalyticꢀactivityꢀunderꢀvisibleꢀlightꢀ ꢀ
Asꢀ shownꢀ inꢀ Fig.ꢀ S9,ꢀ bothꢀ BiOBrꢀ andꢀ crushedꢀ BiOBrꢀ dis‐
playedꢀtypeꢀIVꢀadsorption‐desorptionꢀisothermsꢀwithꢀaꢀdistinctꢀ
hysteresisꢀ loopꢀ characteristicꢀ ofꢀ aꢀ mesoporousꢀ structure.ꢀ Theꢀ
40
BiOBr with crushing
BiOBr
BiOBr
BiOBr without calcination
BiOBr + HB + EG
(
a)
(b)


30
CB
UV
Bi 6p
Vis
2
0
0
0
2
.56 eV
2.66 eV
2
.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
Br 4p
O 2p
h (eV)
VB
BiOBr
1
BiOBr
BiOBr with crushing
200
300
400
500
600
700
800
2
00
300
400
500
600
700
800
Wavelength (nm)
Wavelength( nm)
Fig.ꢀ4.ꢀ(a)ꢀUV‐visꢀDRSꢀofꢀBiOBrꢀandꢀcrushedꢀBiOBr;ꢀinset:ꢀopticalꢀbandgapꢀofꢀBiOBr.ꢀ(b)ꢀNormalizedꢀSPSꢀspectraꢀofꢀBiOBr,ꢀBiOBrꢀwithoutꢀcalcination,ꢀ
andꢀBiOBrꢀ+ꢀEGꢀ+ꢀHB;ꢀinset:ꢀbandgapꢀstructureꢀofꢀBiOBr.ꢀ

ꢀ
YingchunꢀMiaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1411–1417ꢀ
1415ꢀ
5
4
3
2
1
0
0
0
0
0
0
3
2
1
0
0
0
0
(
a)
(b)
BiOBr with crushing
BiOBr
No photocatalyst
Flower-like BiOBr
BiOBr
BiOBr with crushing
0
30
60
90
120
150
180
0
100
200
300
400
500
600
700
Time (min)
Time (min)
(
c)
(d)
1
0
0
0
0
0
.0
.8
.6
.4
.2
.0
1.0
0.8
0.6
0.4
0.2
0.0
BiOBr
BiOBr+BQ
BiOBr+TBA
BiOBr+EDTA
BiOBr+AgNO
3
0
180
360
540
720
900
0
30
60
90
120
150
180
Time (min)
Time (min)
Fig.ꢀ5.ꢀ(a)ꢀComparisonꢀofꢀdifferentꢀmorphologiesꢀofꢀBiOBrꢀatꢀtheꢀnormalizedꢀspecificꢀsurfaceꢀareaꢀinꢀtheꢀphotocatalyticꢀdegradationꢀofꢀRhBꢀunderꢀvisi‐
bleꢀlight;ꢀ(b)ꢀTOCꢀanalysisꢀofꢀBiOBrꢀandꢀcrushedꢀBiOBr;ꢀ(c)ꢀReproducibilityꢀofꢀBiOBr;ꢀ(d)ꢀEffectꢀofꢀdifferentꢀtrappingꢀagentsꢀtoꢀinvestigateꢀtheꢀroleꢀofꢀ
activeꢀradicalsꢀinꢀBiOBrꢀcatalyst.ꢀReactionꢀconditions:ꢀ100ꢀmLꢀRhBꢀaqueousꢀsolutionꢀ10.0ꢀmg/L,ꢀ25.0ꢀmgꢀcatalyst,ꢀ300ꢀWꢀXeꢀlampꢀ(λꢀ>ꢀ420ꢀnm),ꢀandꢀTꢀ=ꢀ
30ꢀ°C.ꢀ
2
BETꢀ surfaceꢀ areaꢀ ofꢀ BiOBrꢀ wasꢀ determinedꢀ toꢀ beꢀ 2.30ꢀ m /g.ꢀ
tocatalystsꢀsuchꢀasꢀBiOXꢀ(Xꢀ=ꢀCl,ꢀBr,ꢀI),ꢀBiVO
Bi ,ꢀBi ,ꢀandꢀbismuthꢀtitanate,ꢀtheyꢀcanꢀbeꢀeasilyꢀreducedꢀtoꢀ
lowꢀvalenceꢀstatesꢀbyꢀphotogeneratedꢀelectrons.ꢀToꢀconfirmꢀtheꢀ
stabilityꢀofꢀBi ꢀinꢀBiOBr,ꢀXPSꢀcharacterizationꢀtestsꢀwereꢀem‐
ployedꢀ (Fig.ꢀ S11).ꢀ Theꢀ XPSꢀ peakꢀ positionꢀ showedꢀ noꢀ obviousꢀ
changes,ꢀfurtherꢀindicatingꢀtheꢀexcellentꢀstabilityꢀofꢀourꢀBiOBrꢀ
photocatalyst.ꢀ
4
,ꢀBi
2
WO
6
,ꢀBi
2
MoO
6
,ꢀ
2
Afterꢀ crushing,ꢀ theꢀ BETꢀ surfaceꢀ areaꢀ increasedꢀ toꢀ 17.3ꢀ m /gꢀ
O
2 3
S
2 3
owingꢀtoꢀtheꢀdecreasedꢀparticleꢀsize.ꢀFromꢀFig.ꢀ5(a),ꢀweꢀcouldꢀ
seeꢀthatꢀnoꢀsignificantꢀdegradationꢀinꢀRhBꢀoccurredꢀinꢀtheꢀab‐
senceꢀofꢀaꢀphotocatalyst.ꢀUnderꢀvisibleꢀlight,ꢀRhBꢀinꢀtheꢀsolutionꢀ
completelyꢀdisappearedꢀafterꢀ180ꢀminꢀofꢀphotocatalysisꢀofꢀBi‐
OBr.ꢀAlthoughꢀcrushedꢀBiOBrꢀexhibitedꢀaꢀmuchꢀhigherꢀspecificꢀ
surfaceꢀareaꢀthanꢀBiOBr,ꢀitsꢀRhBꢀdegradationꢀactivityꢀwasꢀfarꢀ
3+
Toꢀ investigateꢀ theꢀ mechanismꢀ ofꢀ theꢀ photodegradationꢀ ofꢀ
RhB,ꢀweꢀusedꢀdifferentꢀtrappingꢀagentsꢀasꢀscavengers,ꢀincludingꢀ
2
2
weakerꢀ (3.97%/m ꢀ versusꢀ 43.29%/m ꢀ orꢀ 68.68%ꢀ versusꢀ
9.57%).ꢀ Suchꢀ phenomenaꢀ wereꢀ alsoꢀ observedꢀ duringꢀ theꢀ
9
3
ethylenediaminetetraaceticꢀ acidꢀ (EDTA),ꢀ AgNO ,ꢀ tert‐butylꢀ
photocatalyticꢀdegradationꢀofꢀMOꢀ(Fig.ꢀS10).ꢀThisꢀindicatedꢀthatꢀ
theꢀmultistageꢀreflectionꢀofꢀnanosheetsꢀinꢀtheꢀBiOBrꢀmicrocubeꢀ
photocatalystꢀ couldꢀ increaseꢀ lightꢀ absorption,ꢀ narrowꢀ theꢀ
bandgap,ꢀandꢀgenerateꢀmoreꢀphotoelectronsꢀandꢀholes,ꢀleadingꢀ
toꢀenhancedꢀphotocatalyticꢀactivity.ꢀTheꢀconversionꢀrateꢀatꢀ180ꢀ
alcoholꢀ(TBA),ꢀandꢀbenzoquinoneꢀ(BQ),ꢀandꢀexploredꢀtheꢀeffectsꢀ
+
−
ofꢀ photo‐inducedꢀ holesꢀ (h ),ꢀ photogeneratedꢀ electronsꢀ (e ),ꢀ
2−
hydroxylꢀ radicalsꢀ (·OH),ꢀ andꢀ superoxideꢀ anionsꢀ (O ·)ꢀ onꢀ theꢀ
photocatalyticꢀ reactionꢀ system.ꢀ Fig.ꢀ 5(d)ꢀ showsꢀ theꢀ effectꢀ ofꢀ
variousꢀsacrificialꢀagentsꢀonꢀtheꢀphotocatalyticꢀactivity.ꢀItꢀwasꢀ
foundꢀ thatꢀ theꢀ additionꢀ ofꢀ TBAꢀ weaklyꢀ influencedꢀ theꢀ photo‐
catalyticꢀdegradationꢀofꢀRhB,ꢀindicatingꢀthatꢀtheꢀactiveꢀradicalꢀ
·OHꢀdidꢀnotꢀplayꢀaꢀkeyꢀroleꢀinꢀRhBꢀdegradation.ꢀWhenꢀaddingꢀ
2
minꢀwasꢀaboutꢀ99.57%ꢀ(~43.29%/m ),ꢀwhileꢀtheꢀTOCꢀremovalꢀ
(
Fig.ꢀ5(b))ꢀrateꢀwasꢀonlyꢀaboutꢀ12.24%.ꢀTheseꢀresultsꢀindicatedꢀ
thatꢀonlyꢀaꢀsmallꢀfractionꢀofꢀRhBꢀwasꢀcompletelyꢀdegradedꢀandꢀ
mineralizedꢀinꢀCO .ꢀInꢀaddition,ꢀBiOBrꢀshowedꢀsuperiorꢀphoto‐
2−
2
BQꢀtoꢀcaptureꢀ O ·ꢀasꢀanotherꢀactiveꢀradicalꢀintoꢀtheꢀreactionꢀ
system,ꢀtheꢀphotocatalyticꢀactivityꢀdidꢀnotꢀsignificantlyꢀchange.ꢀ
Furthermore,ꢀtheꢀadditionꢀofꢀEDTAꢀconsiderablyꢀdecreasedꢀtheꢀ
photocatalyticꢀdegradationꢀofꢀRhBꢀcomparedꢀtoꢀpristineꢀBiOBr.ꢀ
degradationꢀactivityꢀforꢀRhBꢀthanꢀflower‐likeꢀBiOBrꢀ(BETꢀsur‐
2
faceꢀareaꢀ=ꢀ23.5ꢀm /g,ꢀ[21]),ꢀindicatingꢀthatꢀtheꢀmicrocubicꢀBi‐
OBrꢀ mesocrystalsꢀ facilitatedꢀ chargeꢀ transferꢀ toꢀ improveꢀ theꢀ
photocatalyticꢀ performance.ꢀ Furthermore,ꢀ BiOBrꢀ exhibitedꢀ
excellentꢀstability,ꢀasꢀshownꢀinꢀFig.ꢀ5(c)ꢀwithꢀfiveꢀrecyclesꢀtest‐
ing,ꢀwhichꢀ couldꢀbeꢀ attributedꢀtoꢀitsꢀhighlyꢀcrystallineꢀnatureꢀ
thatꢀ inhibitedꢀ theꢀ decompositionꢀ ofꢀ BiOBr.ꢀ Asꢀ isꢀ wellꢀ known,ꢀ
Inꢀ particular,ꢀ addingꢀ AgNO ꢀ intoꢀ theꢀ photocatalyticꢀ reactionꢀ
3
systemꢀ greatlyꢀ reducedꢀ theꢀ degradationꢀ ofꢀ RhB.ꢀ Itꢀ couldꢀ beꢀ
concludedꢀ thatꢀ theꢀ mainꢀ activeꢀ speciesꢀ wereꢀ theꢀ photogener‐
2
−
atedꢀelectrons,ꢀwhichꢀreactedꢀwithꢀdissolvedꢀO
2
ꢀtoꢀproduceꢀO ·ꢀ
3+
becauseꢀofꢀtheꢀstrongꢀoxidizingꢀabilityꢀofꢀBi ꢀinꢀBi‐basedꢀpho‐
andꢀthenꢀoxidizedꢀpollutants.ꢀ ꢀ

1416ꢀ
YingchunꢀMiaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1411–1417ꢀ
4
.ꢀ ꢀ Conclusionsꢀ ꢀ ꢀ
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[
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Inꢀsummary,ꢀnovelꢀBiOBrꢀmicrocubesꢀwereꢀpreparedꢀbyꢀmi‐
crowave‐assistedꢀ ILꢀ self‐assemblyꢀ throughꢀ hydrogenꢀ
bond‐co‐π‐πꢀ stacking.ꢀ Theꢀ as‐obtainedꢀ BiOBrꢀ exhibitedꢀ highꢀ
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visibleꢀ lightꢀ owingꢀ toꢀ itsꢀ narrowꢀ energyꢀ bandgapꢀ andꢀ strongꢀ
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degradationꢀofꢀpollutantsꢀwereꢀphotogeneratedꢀelectrons.ꢀFur‐
thermore,ꢀ organicꢀ dyesꢀ couldꢀ beꢀ completelyꢀ mineralized,ꢀ
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2
1
微波辅助离子热合成具有高光催化活性的 BiOBr 片层微米立方体
a,b,*
b
b
b,#
缪应纯
, 廉志超 , 霍宇凝 , 李和兴
a
曲靖师范学院资源与环境化学重点实验室, 云南曲靖 655400
b
上海师范大学上海市稀土功能材料重点实验室, 上海 200234
摘要: 微波辅助离子热合成技术因其加热和反应速度快、反应时间短、产物选择性高、环保、节能等优点, 而广泛应用于
纳米棒、纳米线和中空纳米微球等各种形貌功能材料的合成. BiOBr 光催化剂具有毒性低、光生空穴氧化能力强、光降解
活性高等优点, 在光催化降解污染物方面研究非常广泛. 虽然各种形貌的BiOBr 光催化剂可以通过传统的溶剂热法合成,
但仍然需要开发绿色和高效节能的合成方法, 来设计新型结构和高光催化降解活性的BiOBr 光催化剂. 本文首次报道了
由微波辅助离子热自组装的方法合成新型结构的BiOBr 微米立方体. 该BiOBr 由规则的多层纳米片组成, 其通过在Br-端
表面上选择性吸附离子液体形成, 随后形成氢键的π‒π堆叠. 结果显示BiOBr 是由厚度小于50 nm 的纳米片组装成为4
μm 左右的纳米立方块. 其中Bi:Br:O 摩尔比为1:1:1, 表明生成纯化学计量比的BiOBr, 且具有高结晶度的纯四方相. 我们
通过添加不同的表面活性剂, 进一步确认氢键-co-π–π叠层在BiOBr 片层立方块形成中的重要性.
2
将BiOBr 片层立方块研磨粉碎后其BET 表面积为从2.30 急剧增至17.3 m /g, 但其降解RhB 活性却大幅度下降. 由
于纳米片层的层间反射和散射, 有效地提升了BiOBr 的可见光吸收, 光学带隙由2.66 窄化为2.56 eV, 因而具有高的可见
光光降解活性和优异的稳定性及矿化能力. 光催化降解180 min 后, 罗丹明B 的转化率约为99.57%, 而有机碳去除率高达
1
2.24%; 对于磨碎的BiOBr 罗丹明B 的转化率和有机碳去除率分别为68.68% 和8.62%. 光催化反应前后的BiOBr 中,
3
+
Bi 离子的XPS 峰位置没有明显的变化, 进一步表明BiOBr 光催化剂具有较高的稳定性. 这种具有高活性、优异的稳定性
以及高矿化能力的BiOBr, 在实际应用光催化降解染料废水和清洁能源方面显示出很好的潜力. 此外, 通过光催化反应过
+
程中不同捕获剂的添加确定了光降解的主要活性物种. 当加入硝酸银溶液的时候, 由于光生电子快速被Ag 离子捕获, 光
降解活性明显下降. 活性物种的捕获实验表明, 光生电子为主要的活性物种.
关键词: 微波; BiOBr 片状立方体; 自组装; 光催化降解; 矿化能力
收稿日期: 2018-03-03. 接受日期: 2018-04-25. 出版日期: 2018-08-05.
*
通讯联系人. 电子信箱: miaoyingchun1979@sohu.com
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通讯联系人. 电子信箱: hexing-li@shnu.edu.cn
基 金 来 源 : 国 家 自 然 科 学 基 金 (20937003, 21261140333, 21237003, 21207091, 21577092, 2171101231); 上 海 市 政 府 项 目
(
12230706000, 11JC1409000, 12YZ091, 15520711300); 云南省应用基础研究项目 (2013FZ109, 2016FB016); 云南省教育部门重点
项目 (2015Z183, 2016ZZX207).
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).