聚苯胺超级电容器性能(2)

2.4.Preparationofelectrodesandelectrochemicalmeasurement

Theworkingelectrodeswerepreparedbymixing80wt%activematerial,10wt%carbonblack,and10wt%polytetra uoroethylene(PTFE),thenpressedintothindiskswithuniformthickness.Themassloadingoftheactivematerialsoneachelectrodeisabout8mgcm 2.Thesupercapacitorwasconstructedbytwosymmetricworkingelectrodes,sandwichedwithapolypropylene(PP)separa-torand1MaqueousH2SO4asanelectrolyte.Alltheelectrochemicalexperimentsinthisworkwerecarriedoutusingate onswageloktypetwo-electrodecon gurationwithtwostainless-steelsheetsasthecurrentcollector.Cyclicvoltammetry(CV)andelectrochem-icalimpedancespectroscopy(EIS)experimentswereconductedwithaPARSTAT2273/CS130electrochemicalstation;galvanostaticcharge-discharge(CD)curvesandcyclestabilitywereperformedwithLANDCT2001Aatroomtemperature.ThepotentialrangeforCVandCDexaminationsvariedfrom0to0.8V.

3.Resultsanddiscussion

3.1.Morphologyandstructurecharacterizations

Fig.1displayssmall-angleX-raydiffractionpatternsofCMK-3andCMK-3/MnO2compositeswithdifferentMnO2content.TheXRDofpristineCMK-3exhibitsanintensediffractionpeak(100)andtworesolveddiffraction(110)and(200),whichcouldbeassignedtothethreewell-resolvedpeaksofahighlyorderedthreedimensionalhexagonalmesostructure.ThethreediffractionpeakscanalsobeobservedinCMK-3/MnO2-1and-2.However,thescat-teringintensityisdecreasedwithincreasingMnO2loadingintheporechannelsofCMK-3andonlyonepeakof(100)isdetected

in

Fig.1.XRDpowderpatternsof(a)CMK-3,(b)CMK-3/MnO2-1,(c)CMK-3/MnO2-2and(d)CMK-3/MnO2-3.TheinsetistheTEMimageoftheCMK-3/MnO2-2compos-ite.

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Y.Yanetal./ElectrochimicaActa71 (2012) 27–32

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theCMK-3/MnO2-3.Asreportedearlier[26],theinclusionofguestspeciesintotheinternalporesofmesoporousmaterialsresultedinadecreaseinthepeakintensity.Therefore,thisresultindicatesMnO2nanoparticleslocatedinsidethemesopores.

Inordertovisuallycon rmtheexistenceofMnO2intheporechannelsofCMK-3afteroxidation-reductionreaction,TEMimageofCMK-3/MnO2-2compositeisdepictedinFig.1,inset.ThehighlyorderedcarbonnanowiresfeaturethesameperfecthexagonallymesostructuredarraysasthechannelsoftheirmothermoldSBA-15,indicatingtheorderedporechannelswerepreservedwelluponKMnO4treatment.NobulkaggregationofMnO2nanoparticlescanbefoundontheoutersurfaceofCMK-3,andthedarkerarearevealsMnO2nanoparticlesareformedinsideCMK-3duetotheirmuchhigherdensitythancarbon.

ThechemicalstructureofCMK-3andternarycompositewasfur-thercon rmedbyFT-IRspectrashowninFig.2.Twobroadbandsat3455cm 1and1145cm 1areobservedinthecurveofCMK-3,whicharemainlycausedbythestretchingvibrationofandCbonds.AsshowninthecurveofPANI/CMK-3/MnO2-2,thecharacteristicpeaksat1637cm 1and1487cm 1canbeascribedtotheCCstretchingdeformationofquinoidandbenzenerings,respectively[27].Moreover,thecharacteristicabsorptionbandsinthe1200–1400cm 1correspondtotheCNstretchingbandofanaromaticamine.TheabovebandsindicatethatPANIchainsareformedintheternarycomposite.Inaddition,thebandsintheregionsfrom400to800cm 1canbeassignedtoMnstretchingvibrations,furtherindicatingtheexistenceofMnO2intheternarycomposite[28].

ThemorphologiesofPANI,PANI/CMK-3,PANI/CMK-3/MnO2-2andPANI/CMK-3/MnO2-3compositeswerecharacterizedbyFE-SEMaspresentedinFig.3.AscanbeseenfromFig.3a, ber-like

Fig.2.FTIRspectraof(a)CMK-3and(b)PANI/CMK-3/MnO2-2ternarycomposite.

PANIparticlesareaggregatedtogether,whilethePANI/CMK-3compositehasroughsurfacesduetoPANIdepositedonthecar-bonmatrix(Fig.3b).ThePANI/CMK-3/MnO2-2ternarycompositeobservedinFig.3cexhibitsthesimilarmorphologytoPANI/CMK-3,andparticularly,depositedPANIchainsformamoreuniformnano-layerthanthoseinPANI/CMK-3.DuetotheroleofMnO2,theinteractionbetweenthequinoidringofPANIandtheCMK-3/MnO2canbestabilized[29],whichfavorsPANIchainstobeadsorbeduniformlyonthesurfaceofCMK-3/MnO2.InthecaseofPANI/CMK-3/MnO2-3(Fig.3d),uniformPANIlayercanalsobeobserved.With

Fig.3.FE-SEMimagesof(a)PANI,(b)PANI/CMK-3,(c)PANI/CMK-3/MnO2-2,and(d)PANI/CMK-3/MnO2-3.

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30Y.Yanetal./ElectrochimicaActa71 (2012) 27–32

Fig.4.Galvanostaticcharge-dischargecurvesof(a)PANI/CMK-3/MnO2-1,(b)PANI/CMK-3/MnO2-2,and(c)PANI/CMK-3/MnO2-3atacurrentdensityof0.3Ag 1withinthepotentialwindow0–0.8V.

increasingconcentrationofKMnO4aqueoussolution,morecarbonsiteswereoxidizedandahighportionofMnO2was lledintheporesofCMK-3.Therefore,thoughthePANIcontentisthesameinbothternarycomposites,bulk ber-shapedPANIparticlesarefoundinPANI/CMK-3/MnO2-3composite.

3.2.Electrochemicalproperties

Toinvestigatetheelectrochemicalperformanceoftheresultingternarycompositesaselectrodesforsupercapacitors,thegalvanos-taticcharge-dischargecurvesweremeasuredatacurrentdensityof0.3Ag 1withinthepotentialwindow0–0.8V(Fig.4).Thespeci ccapacitance(SC)ofelectrodematerialwascalculatedaccordingtothefollowingequation:

C2(I×t)=

where1Cisspeci ccapacitance(Fg ),Iisthecharge–dischargecurrent(A),tisthedischargetime(s),misthemassofactivemate-rial(g)withinoneelectrodeand Vistheworkingvoltage(V).ThecalculatedSCis652,695and473Fg 1forPANI/CMK-3/MnO2-1,PANI/CMK-3/MnO2-2andPANI/CMK-3/MnO2-3,respectively.Apparently,withtheincreasingofMnO2content,theSCoftheternarycompositesisenhancedasaresultoftheeffectiveelec-trochemicalutilizationofMnO2;whereasitstartstodecreasewithanexcessincreaseintheMnO2content(e.g.21%)duetothelowutilizationoftheactivematerialcausedbythepresenceofmassbulkPANIparticlesinPANI/CMK-3/MnO2-3composite.

Tofurthercon rmtheadvantageoftheternarycompositeintheeffectiveelectrochemicalutilizationofMnO2,charge-dischargecurvesofpurePANI,PANI/CMK-3/MnO2-2andPANI/CMK-3wereshowninFig.5a.ItisobviousthatbulkPANIexhibitsthepoorestelectrodeperformanceandtheSCisonly254Fg 1duetothebulkparticlesleadingtothelowsurfacearea.ForPANI/CMK-3composite,thenanolayerofPANIcoatedontheCMK-3facili-tatestheutilizationofthePANIandtheSCofbinarycompositecanreach587Fg 1.AsforPANI/CMK-3/MnO2-2composite,itpossessesthehighestSCof695Fg 1.TheenhancedSC …… 此处隐藏：6046字，全部文档内容请下载后查看。喜欢就下载吧 ……