Demonstration of Superiority of the Marcus–Hush Electrode Kinetic Model in the Electrochemistry of Dissolved Decamethylferrocene at a Gold-Modified Electrode by Fourier-Transformed Alternating Current Voltammetry

Abstract

Fourier-transformed alternating current (AC) voltammetry is used to compare the applicability of the Butler−Volmer (BV) and Marcus−Hush (MH) models of electrode kinetics (k 0 ) to an outer-sphere electrode process where both oxidized and reduced species are soluble. According to numerical simulations, differences between the two models can be revealed clearly by analysis of the AC harmonics when the values of k 0 and reorganization energy are sufficiently small. Experimentally a Au electrode coated with a self-assembled octanethiol monolayer was introduced to decrease the rate of the DmFc 0/+ (DmFc = decamethylferrocene) process, a well-known outer-sphere process in a propylene carbonate solution containing 0.10 M tetrapropylammonium tetrafluoroborate. Based on a comparison of the computationally generated best fits, it was demonstrated that the MH model provides substantially better agreement with the experimental data than the BV model for the DmFc 0/+ process, unlike some other examples in the literature that favor the BV model.

A perceived paucity of quantitative studies in the modern era of voltammetry: prospects for parameterisation of complex reactions in Bayesian and machine learning frameworks

“…Thus, the 'odds' for each model being compared are updated as more information becomes available. We have used this 'updating the odds' approach by treating each of the harmonics obtained in an AC voltammetric experiment as providing new information [40] and confirmed that use of the Marcus-Hush model is superior for one particular electrode process [40] where this had been suggested previously on the basis of analysis by conventional data optimisation [41]. Intriguingly, even though the attributes of computersupported data analysis in DC voltammetry have been established and even reviewed by Speiser [42], the importance of quantifying confidence limits and reporting parameter estimates emanating from a comparison of experimental and simulated data seems to be absent as a routine aspiration in voltammetry.…”

Application of Bayesian Inference in Fourier-Transformed Alternating Current Voltammetry for Electrode Kinetic Mechanism Distinction

“…35,36 We have previously reported the use of FTACV to assess the applicability of the BV and MH models by studying the electrode kinetics of the DmFc 0/+ process in propylene carbonate at an octanethiolmodified Au electrode. 21 On the basis of the LS analysis, the MH model (LS = 94.3%) was shown to provide better agreement with the experimental data than the BV model (LS = 76.5%). However, comparison of LS values does not provide information on exactly how preferential the MH model is relative to the BV one.…”

“…Summary of the Bayesian Analysis Protocol Applied to MH and BV Models for Oxidation of DmFc in Propylene Carbonate at a Gold-Modified Electrode21 …”

“…In this form of analysis, the outcome depends on the experience and prejudices of the experimenter to determine what combination of parameters provides the best agreement between experimental and simulated data. As computing power has increased, more advanced digital approaches have become available to overcome human-factor limitations by performing theory-experiment comparisons automatically. − In these data optimization procedures, each parameter of interest is assigned a set of values (e.g., from 0.01 to 1 cm s –1 and from 0.4 to 0.6), and a wide range of combinations are used for comparison with experiment. A least-squares (LS) function is then used to gauge the level of agreement between experiment and the simulated data for each parameter set, with the best fit having the minimal LS value.…”

Impact of sp2 Carbon Edge Effects on the Electron-Transfer Kinetics of the Ferrocene/Ferricenium Process at a Boron-Doped Diamond Electrode in an Ionic Liquid

“…[42][43] In brief, a single barrel micropipette was pulled to ≈50 µm tapered end, filled Theory-experiment comparison. Since negligible differences are expected between Butler-Volmer (BV) and Marcus-Hush theories in simulations when the electron transfer kinetics are relatively fast, as applies to the Fc 0/+ process studied in this paper, 44 the simpler BV theory was used in all simulations. Simulating the simple one-electron transfer reaction given in Equation…”