AC and Electrohydrodynamic Impedances for a Chemical Preceding Electrochemical Mechanism I. Theory

Analytically accurate solutions for the ac impedance and the electrohydrodynamic (EHD) impedance have been calculated for a chemical electrochemical mechanism occurring on a rotating disk electrode. Schmidt number corrections were considered. These analytical expressions have been compared to a direct numerical integration by the finite difference method and the divergence found was less than 1% (ac impedance) and less than 4% (EHD impedance) in a wide range of rate constant values for the preceding chemical reaction. The aim of this treatment was to obtain an alternative to numerical treatments which are time consuming, suitable for fitting procedure of impedance data which require a large number of elementary calculations of the impedance value, while keeping a good accuracy compatible with the experimental errors.