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

摘要

In transient forms of voltammetry, quantitative analysis of electrode kinetics and parameters such as uncompensated resistance (R_u) and double layer capacitance (C_(dl)) 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 (0.1 M Bu_4NPF_6) at a glassy carbon electrode using higher order harmonics available in Fourier transformed ac voltammetry implied that the heterogeneous charge transfer rate constant k_0 is ≥0.25 cm s~(-1) with the charge transfer coefficient (a) 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 IR_u (Ohmic drop) on these parameters. For example, computation of contour maps based on a sweep of two sets of parameters such as k_0 and R_u or a and k_0 imply that a is 0.50 ± 0.05 and that k0 lays in the range 0.2–0.4 cm s~(-1) with R_u around 130 Ohm. Quantitative evaluation of k_0, a and R_u for the quasi-reversible [Fe(CN)_6]~(3-) + e l harp over r [Fe(CN)_~(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 k_0 for the electrode process lies close to 0.010 cm s~(-1), a is 0.50 ± 0.05 and R_u is ≤10 Ohm.