Inappropriate Use of the Quasi-Reversible Electrode Kinetic Model in Simulation-Experiment Comparisons of Voltammetric Processes That Approach the Reversible Limit

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• 作者：Alexandr N. Simonov ; Graham P. Morris ; Elena A. Mashkina ; Blair Bethwaite ; Kathryn Gillow ; Ruth E. Baker ; David J. Gavaghan ; Alan M. Bond
• 刊名：Analytical Chemistry
• 出版年：2014
• 出版时间：August 19, 2014
• 年：2014
• 卷：86
• 期：16
• 页码：8408-8417
• 全文大小：406K
• ISSN：1520-6882

文摘

Many electrode processes that approach the 鈥渞eversible鈥?(infinitely fast) limit under voltammetric conditions have been inappropriately analyzed by comparison of experimental data and theory derived from the 鈥渜uasi-reversible鈥?model. Simulations based on 鈥渞eversible鈥?and 鈥渜uasi-reversible鈥?models have been fitted to an extensive series of a.c. voltammetric experiments undertaken at macrodisk glassy carbon (GC) electrodes for oxidation of ferrocene (Fc^0/+) in CH₃CN (0.10 M (n-Bu)₄NPF₆) and reduction of [Ru(NH₃)₆]³⁺ and [Fe(CN)₆]^{3鈥?/sup> in 1 M KCl aqueous electrolyte. The confidence with which parameters such as standard formal potential (E0), heterogeneous electron transfer rate constant at E0 (k0), charge transfer coefficient (伪), uncompensated resistance (R_u), and double layer capacitance (C_DL) can be reported using the 鈥渜uasi-reversible鈥?model has been assessed using bootstrapping and parameter sweep (contour plot) techniques. Underparameterization, such as that which occurs when modeling C_DL with a potential independent value, results in a less than optimal level of experiment-theory agreement. Overparameterization may improve the agreement but easily results in generation of physically meaningful but incorrect values of the recovered parameters, as is the case with the very fast Fc0/+ and [Ru(NH₃)₆]3+/2+ processes. In summary, for fast electrode kinetics approaching the 鈥渞eversible鈥?limit, it is recommended that the 鈥渞eversible鈥?model be used for theory-experiment comparisons with only E0, R_u, and C_DL being quantified and a lower limit of k0 being reported; e.g., k0 鈮?9 cm s鈥? for the Fc0/+ process.}