电极反应动力学介绍

Chap5IntroductiontoKineticsofElectrodeReactions5.1HomogeneousReactionsKCCkkABbfABkfkbdynamicequilibriumvf=kfCAvb=kbCBvnet=kfCA-kbCBatequilibrium:vnet=0kfCA=kbCBv0=kf(CA)eq=kb(CB)eqexchangevelocityRTEAAekArrheniusEquationA:frequencyfactorEA:activationenergykfkbO+neRatequilibrium:**'0lnROCCnFRTEEnFAitCkvCOff),0(nFAitCkvaRbb),0(5.2ElectrodeReactionsnFAitCktCkvvvRbOfbfnet),0(),0()],0(),0([tCktCknFAiiiRbOfac)()1(0'0EEnfbekk)(0'0EEnffekkf=F/RTk0:standardrateconstant:transfercoefficient0.3~0.7]),0(),0([)()1()(0'0'0EEnfREEnfOetCetCnFAkiButler–Volmerequation5.3ExchangeCurrentatequilibrium:inet=0)()1(0)(0'0'0),0(),0(EEnfREEnfOetCnFAketCnFAkCO(0,t)=CO*CR(0,t)=CR***'0lnROeqCCnFRTEEi0=ic=ia(E=Eeq)exchangecurrent*)1*(00ROCCnFAkiCO*=CR*=CCnFAki005.4Current–OverpotentialEquation=E–EeqoverpotentialnfRRnfOOeCtCeCtCii)1(**0),0(),0(cathodiccurrentanodiccurrent1.NoMassTransferEffectwellstirredlowcurrent(i10%iLaori10%iLc)CO(0,t)≈CO*CR(0,t)≈CR*][)1(0nfnfeeii(a)j0=10-3A/cm2(b)j0=10-6A/cm2(c)j0=10-9A/cm22.LinearCharacteristicatSmallex≈1+xwhenxissmalli≈i0(-nf)whenissmallCTRnFiRTnfii001chargetransferresistance3.TafelBehavioratLargeatlargenegativeoverpotentials:exp(-nf)exp[(1-)nf]nfeii0Tafelequation4.VeryFacileKineticsandReversibleBehavior),0(),0(ln'0tCtCnFRTEERO0reversible5.EffectsofMassTransfersmallRmt:masstransferresistancei0/il