清华大学博士论坛会议论文集14

ElectrochemicalfabricationofCuAl2O4-CuhybridnanorodsatroomtemperatureDingDa-wei1,CaiWei-min1,2*,LongMing-ce1,WuYa-hui3（1.SchoolofEnvironmentalScienceandEngineering,ShanghaiJiaoTongUniversity,Shanghai200240,China;2.StateKeyLaboratoryofUrbanWaterResourceandEnvironment,HarbinInstituteofTechnology,Harbin150090;3.DepartmentofEnvironmentalScienceandEngineering,SchoolofCivilandEnvironmentalEngineering,HarbinInstituteofTechnology,Harbin150090,China）Abstract:Amongvariousmethodsusedforfabricationofnanoarrays,templatesynthesisusingelectrodepositonhasbeenprovedalowcostandhighyieldtechniqueforproducinglargearraysofnanowiresornanorods.Herein,wepresentanelectrochemicalfabricationofCuAl2O4-Cuhybridnanorodarraysinorderedanodicaluminumoxide(AAO)filmnanotubes.ThenucleationandgrowthofCuAl2O4nanocrystallitewasfavoredbyacomfortableelectro-chemicalenvironment,especially,theappliedpotential,whichwasinvestigatedindetails.ThediameterofthenanorodswasinaccordancewiththesizeofAAOnanotube(40-50nm),withlengthsof600to700nm.PhotocatalysisexperimentoftheassynthesizedCuAl2O4-Cuhybridarraysshowedconsiderabledegradationrateofmethylorangeundervisible-lightirradiation,whichrenderedpotentialapplicationforthedegradationofotherrecalcitrantorganicpollutantsinwaterpurification.Keywords:spinel,CuAl2O4-Cuhybrid,templatesynthesis,photocatalysisIntroductionLowdimensionalspinelcompoundshavedrawnconsiderableattentionfortheirwidevarietyoftechnologicalapplicationsinelectronic,catalytic,andmagneticproperties(AmmundsenandPaulsen2001;Ludersetal.2006;Zhangetal.2005;Jeongetal.2007;Nasr-Allah2002;Dhak2006).Aluminumbasedspinelsconstituteanimportantclassofitskind.Copperaluminate,CuAl2O4,iswellknowntobeaninversespinelandpossessesinterestingelectronicandcatalyticpropertiesandisfoundwideapplicationasceramicpigments,coatingsandcatalysts(Alejandreetal.1999;Shimizu2000;Kim2001;Yahiro2006).Byfar,anumberofapproacheshavebeenreportedforthesynthesisofnanocrystallineCuAl2O4powders:solidstatereaction(L.C.Leu2007),co-precipitationreactioninsolution(Shimizu2000;Kameswari1996)，combustionprocess(Mimani2001)andsol-geltechnique(Yanyan2007;Meyeretal.1999)havebeenused.Nevertheless,alltheeffortstoprepareCuAl2O4spinelmentionedaboverequirehigh-temperature(T800℃)calcinationproceduresandtheproductislimitedtopowersorfilm(Dhak2006;Yahiro2006).Alow-cost,easy-preparednewsynthesismethodisthereforeofgreatattractionconsideringthemorphologycontrolandenergyconserving.Previously,wehavereportedbrieflythesuccessfulsynthesisofnano-scaleCuAl2O4spinelsbyelectrochemicalmethodatroomtemperature.Thisnanorod-likeCuAl2O4-Cuhybridwasfoundgrowwithwellcontrolledmorphologyintheanodicaluminumoxidenanotube(Dingetal.2009).ThenucleationofcrystallineCuAl2O4wasfavoredbyacomfortableelectro-chemicalenvironment,ofwhichelectropotentialwasvitalforthestablegrowthofCuAl2O4crystalswithinconfineddimension.Herein,wediscussedindetailshowpotentialinfluencethedepositionofspinelCuAl2O4intothetubularstructure.Later,excellentsolarspectrummatchingpropertiesandphotocatalyticactivityundervisiblelightirradiationofthemodifiedhybridstructurewaspresented.Thephotocatalyticpropertiesofthenanorodswereinvestigatedbyusingmethylorangeasmodeldye.1Materialsandmethods1.1PreparationofanodicaluminaAluminumfoil(99.99%),0.3-mmthick,isannealedinairat500℃for4hinfurnace.Alpieces,3cm×3cminsize,weredegreasedbyacetoneinultrasonicfor5min,rinsedindistilledwaterandelectropolishedinamixtureofethanolandperchloricaciduntilvisuallymirror-likesurfaceat20V.Priortoanodization,thebackandedgesofelectrodesweresealedwithwaxtoproduceanelectrodewithonlyonefaceexposed.Anodizationwascarriedoutina2Mphosphoricacidat20℃for20minunderavoltageof15Vagainstagraphitecounterelectrode.Thisprocedureproducesaporousaluminumoxidelayerofporefractionabout40%byvolume.Thealuminathicknesswasabout700nmwithporediameterapproximateto50nm.1.2SynthesisofCuAl2O4-CunanorodsUsingatwo-electrodesystemconsistingofagraphiteplateasthecounterelectrodeandPAOastheworkingelectrode,electrochemicaldepositionofCuAl2O4-CuisperformedinanelectrolyteofCuSO4(35g/L)andMgSO4(20g/L)(pH=3~4)atvariouspotentials,respectively,11V,13Vand15Vundercontinuousacmodefor60seconds,frequencywaskeptat200Hzforallsamples.TheelectrolytewasrefreshedaftereveryfivesamplestocompensateCu2+depletionandtokeepthepHvaluesat3~4.1.3PhotocatalysisexperimentTheCuAl2O4-CunanorodsfilledPAOwasfirstlyimmersedina0.5MNaOHat30℃for3minutestoremovetheouteraluminananostructure.TheexposedCuAl2O4-Cunanorodswithanactiveareaof1.2cm2wereplacedinasinglequartzphotoreactor.15mL,5mg/Lmethylorange(MO)wasaddedandstirredcontinuously.AUVlightfiltered350WUV-VisXenonlamp(λ=0.4-1μm)withmaximallightintensityof90mW/cm2wasusedaslightsource.ConcentrationofMOafterdegradationwasmeasuredbyspectrometerattheabsorptionpeakofMO(λ=465nm).ThedegradationrateVwascalculatedwithV=(C0-Ct)/C0×100%,whereC0andCtaretheabsorbanceoforiginalsolutionandsolutionphotodegradedafterttime.2Resultsanddiscussion2.1InfluenceofappliedpotentialFigure1ashowsascanningelectronmicroscope(SEM)imageoftheas-electrodepositedPA