Selective preparation of Bi2O3 visible light-driven photocatalyst by dispersant and calcination

SelectivepreparationofBi2O3visiblelight-drivenphotocatalystbydispersantand

calcination

LijunCheng,YongKang

SchoolofChemicalEngineeringandTechnology,TianjinUniversity,Tianjin300072,China

articleinfoabstract

Bi2O3visiblelightresponsivephotocatalystsweresynthesizedbychemicalprecipitationandconsequentcalcinationprocess.Theas-preparedsampleswerecharacterizedwithXRD,FESEM,UV–st,N-dopedb-Bi2O3withaveragelengthofabout252nmwasselectivelyfabricatedundertheoptimalpreparationconditionsobtainedbyinvestigatingin uenceofdispersanttype,dispersantdosage,calcinationtemper-atureandtimeonBi2O3crystallinephase,morphologyandotherperformances.Thephotocatalysthadstrongabsorptionforvisiblelightandef cientseparationofchargecarrier,whichmadeitagoodphoto-catalysttowardsdegradationofmalachitegreen.Approximately96.5%ofmalachitegreenwasdegradedafterilluminationfor300min.

Ó2013ElsevierB.V.Allrightsreserved.

Articlehistory:

Received2May2013

Receivedinrevisedform2August2013Accepted2August2013

Availableonline12August2013Keywords:Bi2O3

PhotocatalystN-dopedb-Bi2O3Dispersant

1.Introduction

Toutilizesolarenergyef ciently,developingnarrowbandgapvisiblelightresponsivephotocatalysthasattractedconsiderableinterestinphotocatalytic eld.

AmongvariousvisiblelightresponsivephotocatalystssuchasCdS[1,2],WO3[3,4]andFe2O3[5,6],Bi2O3hasbeenwidelyinves-tigatedforitssmallbandgapandstability[7–10].

Inrecentyears,considerablestudieshavefocusedonsynthesisofBi2O3photocatalystswithcontrollablemorphologiesbecauseofstrongrelationshipbetweentheirmorphologiesandtheirphotocatalyticactivities[11–13].Muruganandhametal.fabricatedbarlikebismuthoxalate(Bi2(C2O4)3Á7H2O)andmicrorod-likehy-dratedbismuthoxalate((BiOHC2O4)2ÁH2O)byhydrothermalpro-cesseswithdifferentsolventandobtainedvariousmorphologicala-Bi2O3bycalcinatingtheabovebismuthoxalatesatdifferenttemperature.PhotocatalyticdegradationofAcidOrange7(AO7)dyeindicatedthatthehoneycombbrushlikea-Bi2O3synthesizedbysinteringhydratedbismuthoxalateat300°Cwasthemostef -cient[11].TherearealsoreportsaboutcontrollablepreparationofBi2O3photocatalystsviaadjustingdispersantdosage[12,13].Forexample,Zhangetal.preparedgranularnanocrystalliteBi2O3inpresenceofpolyvinylpyrrolodone(PVP)surfactantandmicrosizedBi2O3rodswithoutPVP,degradationofmethylorange(MeO)showedthatthephotocatalystpreparedinpresenceofPVPhadbetterphotocatalyticactivitythanthatpreparedwithoutthesur-factant[12].Chenetal.fabricatedaseriesofBi2O3photocatalystsCorrespondingauthor.Tel.:+862227408813;fax:+862227403389.

E-mailaddress:ykang@(Y.Kang).

0925-8388/$-seefrontmatterÓ2013ElsevierB.V.Allrightsreserved./10.1016/j.jallcom.2013.08.010

underdifferentpHvaluesanddifferentdosesoflysinedispersantandstudiedeffectofthesesynthesisparametersonmorphologyoftheas-preparedsamples.Measurementofphotocatalyticactiv-itybydegradingRhBindicatedthatmesh-likenano akesBi2O3ob-tainedbyadding6mmollysineandadjustingpHto8.4showedthebestphotocatalyticactivity[13].WeiLiproposedasimplemethodtopreparesphericalmonodisperseBi2O3nanoparticlesinpresenceofpolyethyleneglycol(PEG4000)dispersantunderlowtemperatureanddiscussedin uenceofpreparationconditionssuchasconcentrationofBi(NO3)3anddispersant,reactiontemper-atureandtimeontheshapeandsizedistributionofBi2O3,butitsphotocatalyticactivitywasnotinvestigated[14].Therefore,toim-provethephotocatalyticperformanceofBi2O3bydispersantasamorphologymodi erandto rstproposeeffectofPEGonitsmor-phologyandotherperformancesrelatedtoitsphotocatalyticactiv-ity,PEGwithdifferentmolecularweight(PEG1000,4000,6000)wereusedasdispersanttoselectivelyprepareBi2O3withappropri-ateparticlesize.

Inadditiontomorphology,crystallinephaseofBi2O3iscloselyrelatedtoitsphotocatalyticactivityaswell.Huangetal.synthe-sizedamorphousb-Bi2O3nanoparticlesvialiquidphasemicrowavereactionandgraduallychangedtowellcrystallizedsheet-likenanoparticlesofb-Bi2O3bycalcinatingat300°Canda-Bi2O3at350°C.Thephotocatalyticactivityofb-Bi2O3fordegradationofRhBwasevidentlyhigherthanthatofa-Bi2O3[15].Qiuetal.pre-pareda-andb-Bi2O3nanowiresbyanoxidativemetalvapourtransportdepositiontechniqueandalsofoundthatb-Bi2O3nanowiresshowedhigherphotocatalyticactivitythana-Bi2O3nanowires[16].Ascrystallinephaseisdirectlydeterminedbycal-cinationtemperature,therelevantcalcinationparameterswere