Resistance, Capacitance, and Electrode Kinetic Effects in Fourier-Transformed Large-Amplitude Sinusoidal Voltammetry: Emergence of Powerful and Intuitively Obvious Tools for Recognition of Patterns of
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- 作者：Anna A. Sher ; Alan M. Bond ; David J. Gavaghan ; Kathryn Harriman ; Stephen W. Feldberg ; Noel W. Duffy ; Si-Xuan Guo ; and Jie Zhang
- 刊名：Analytical Chemistry
- 出版年：2004
- 出版时间：November 1, 2004
- 年：2004
- 卷：76
- 期：21
- 页码：6214 - 6228
- 全文大小：894K
- 年卷期：v.76,no.21(November 1, 2004)
- ISSN：1520-6882
文摘
Large-amplitude sinusoidal ac voltammetric techniques,when analyzed in the frequency domain using the Fouriertransform-inverse Fourier transform sequence, producethe expected dc and fundamental harmonic ac responsesin addition to very substantial second, third, and higherac harmonics that arise from the presence of significantnonlinearity. A full numerical simulation of the process,Red 
Ox + e-, incorporates terms for the uncompensated resistance (Ru), capacitance of the double layer(Cdl), and slow electron transfer kinetics (in particular,the reversible potential (E
), rate constant (k0), and chargetransfer coefficient (
) from the Butler-Volmer model).Identification of intuitively obvious patterns of behavior(with characteristically different sensitivity regimes) in dc,fundamental, and higher harmonic terms enables simpleprotocols to be developed to estimate Ru, Cdl, E, k0, and. Thus, if large-amplitude sinusoidal cyclic voltammograms are obtained for two concentrations of the reducedspecies, data obtained from analysis of the recoveredsignals provide initial estimates of parameters as follows: (a) the dc cyclic component provides an estimateof E (because the Ru and k0 effects are minimized); (b)the fundamental harmonic provides an estimate of Cdl(because it has a high capacitance-to-faradaic currentratio); and (c) the second harmonic provides an estimateof Ru, k0, and (because the Cdl effect is minimized).Methods of refining the initial estimates are then implemented. As a check on the fidelity of the parameters(estimated on the basis of an essentially heuristic approach that solely utilizes the dc, fundamental, andsecond harmonic voltammograms), comparison of thepredicted simulated and experimental third (or higher)harmonic voltammograms can be made to verify thatagreement between theory and experiment has beenachieved at a predetermined level. The use of the heuristicpattern recognition approach to evaluate the oxidation offerrocene at a platinum electrode (a reversible process)in the very high resistance solvent dichloromethane (0.1M Bu4NPF6) and the reduction of [Fe(CN6)]3- at a glassycarbon electrode (a quasi-reversible process) in muchlower resistance but higher capacitance conditions foundin aqueous (0.5 M KCl) media is described and verifiesthe inherent advantages of employing large-amplitudesinusoidal techniques in quantitative studies of electrodeprocesses.
Ox + e-, incorporates terms for the uncompensated resistance (Ru), capacitance of the double layer(Cdl), and slow electron transfer kinetics (in particular,the reversible potential (E), rate constant (k0), and chargetransfer coefficient () from the Butler-Volmer model).Identification of intuitively obvious patterns of behavior(with characteristically different sensitivity regimes) in dc,fundamental, and higher harmonic terms enables simpleprotocols to be developed to estimate Ru, Cdl, E, k0, and. Thus, if large-amplitude sinusoidal cyclic voltammograms are obtained for two concentrations of the reducedspecies, data obtained from analysis of the recoveredsignals provide initial estimates of parameters as follows: (a) the dc cyclic component provides an estimateof E (because the Ru and k0 effects are minimized); (b)the fundamental harmonic provides an estimate of Cdl(because it has a high capacitance-to-faradaic currentratio); and (c) the second harmonic provides an estimateof Ru, k0, and (because the Cdl effect is minimized).Methods of refining the initial estimates are then implemented. As a check on the fidelity of the parameters(estimated on the basis of an essentially heuristic approach that solely utilizes the dc, fundamental, andsecond harmonic voltammograms), comparison of thepredicted simulated and experimental third (or higher)harmonic voltammograms can be made to verify thatagreement between theory and experiment has beenachieved at a predetermined level. The use of the heuristicpattern recognition approach to evaluate the oxidation offerrocene at a platinum electrode (a reversible process)in the very high resistance solvent dichloromethane (0.1M Bu4NPF6) and the reduction of [Fe(CN6)]3- at a glassycarbon electrode (a quasi-reversible process) in muchlower resistance but higher capacitance conditions foundin aqueous (0.5 M KCl) media is described and verifiesthe inherent advantages of employing large-amplitudesinusoidal techniques in quantitative studies of electrodeprocesses.