Estimation of electrode kinetic and uncompensated resistance parameters and insights into their significance using Fourier transformed ac voltammetry and e-science software tools

Abstract

In transient forms of voltammetry, quantitative analysis of electrode kinetics and parameters such as uncompensated resistance (Ru) and double layer capacitance (Cdl) are usually undertaken by comparing experimental and simulated data. Commonly, the skill of the experimentalist is heavily relied upon to decide when a good fit of simulated to experimental data has been achieved. As an alternative approach, it is now shown how data analysis can be based on implementation of e-science software tools. Previously, a standard heuristic data analysis approach applied to the oxidation of ferrocene in acetonitrile (0.1M Bu4NPF6) at a glassy carbon electrode using higher order harmonics available in Fourier transformed ac voltammetry implied that the heterogeneous charge transfer rate constant k0 is ⩾0.25cms−1 with the charge transfer coefficient (α) lying in the range of 0.25–0.75. Application of e-science software tools to the same data set allows a more meaningful understanding of electrode kinetic data to be provided and also offers greater insights into the sensitivity of the IRu (Ohmic drop) on these parameters. For example, computation of contour maps based on a sweep of two sets of parameters such as k0 and Ru or α and k0 imply that α is 0.50±0.05 and that k0 lays in the range 0.2–0.4cms−1 with Ru around 130Ohm. Quantitative evaluation of k0, α and Ru for the quasi-reversible [Fe(CN)6]3-+e⇌[Fe(CN)6]4- process at a glassy carbon electrode in aqueous media is also facilitated by use of e-science software tools. In this case, when used in combination with large amplitude Fourier transformed ac voltammetry, it is found for each harmonic that k0 for the electrode process lies close to 0.010cms−1, α is 0.50±0.05 and Ru is ⩽10Ohm.