Cyclic-voltammetry-on-electrode-surfaces-covered-with-porous

SensorsandActuatorsB133(2008)462–466ContentslistsavailableatScienceDirectSensorsandActuatorsB:Chemicaljournalhomepage:www.elsevier.com/locate/snbCyclicvoltammetryonelectrodesurfacescoveredwithporouslayers:Ananalysisofelectrontransferkineticsatsingle-walledcarbonnanotubemodifiedelectrodesIanStreeter,GregoryG.Wildgoose,LidongShao,RichardG.Compton∗PhysicalandTheoreticalChemistryLaboratory,OxfordUniversity,SouthParksRoad,OxfordOX13QZ,UnitedKingdomarticleinfoArticlehistory:Received21January2008Accepted5March2008Availableonline22March2008Keywords:CarbonnanotubesThinlayerdiffusionCyclicvoltammetryHeterogeneousrateconstantsNumericalsimulationabstractCyclicvoltammetryisrecordedoftheoxidationofferrocyanideonaglassycarbonelectrodemodifiedwithmultiplelayersofsingle-walledcarbonnanotubes.Thecurrentresponseisinterpretedintermsofsemi-infiniteplanardiffusiontowardsthemacro-electrodesurfaceandintermsofoxidationoftheelectroactivespeciestrappedinpocketsinbetweenthenanotubes.Athinlayermodelisusedtoillustratetheeffectsofdiffusionwithinaporouslayer.Itisfoundthatasemi-infiniteplanardiffusionmodelaloneisnotappropriateforinterpretingthekineticsoftheelectrontransferatthiselectrodesurface.Inparticular,cautionshouldbeexercisedinrespectofcomparingvoltammetricpeak-to-peakpotentialseparationsbetweennakedelectrodesandnanotube-modifiedelectrodesfortheinferenceofelectrocatalysisviaelectrontransferviathenanotubes.©2008ElsevierB.V.Allrightsreserved.1.IntroductionThepioneeringworkofWangetal.[1]hasledtoextensivelit-erature[2–21]inwhichelectrodes,often,butnotalways,madeofglassycarbon,aremodifiedwithlayersofcarbonnanotubes,andusedtostudytheredoxbehaviourofmoleculesofinterest.TheuseofthesemodifiedelectrodeshasbeenreviewedinRefs.[22–24].Typically‘fasterelectrodekinetics’arereportedonthemodifiedelectrodesandthisiscommonlyinterpretedintermsof‘electro-catalysis’causedbythenanotubes.Thediagnosticcriterionforthefasterelectrodekineticsisoftensimplybasedonthepeak-to-peakpotentialseparationoftheforwardandreversewav