AC and electrohydrodynamic impedances for a chemical preceding electrochemical mechanism I. Theory

Analytically accurate solutions for the ac impedance and the electrohydrody namic (EHD) impedance have been calculated for a chemical electrochemical m echanism occurring on a rotating disk electrode. Schmidt number corrections were considered. These analytical expressions have been compared to a dire ct 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. T he aim of this treatment was to obtain an alternative to numerical treatmen ts which are time consuming, suitable for fitting procedure of impedance da ta which require a large number of elementary calculations of the impedance value, while keeping a good accuracy compatible with the experimental erro rs. (C) 2000 The Electrochemical Society. All rights reserved.