Value of the exponential current–time perturbation for achieving stationary polarisation curves at planar and spherical electrodes of any size

Abstract

Stationary current–potential ( I– E) polarisation curves (SPCs) are of interest in electrochemistry, because the extraction of thermodynamic and kinetic information from such curves is easy. In order to obtain the SPCs under pure diffusion transport conditions, experiments are usually performed using spherical electrodes, at which the SPCs are rapidly attained. A purely diffusional steady state cannot be achieved at planar electrodes. However, the theoretical analysis presented in this work reveals that in the case of chronopotentiometry with exponential current–time perturbation, the Nernst diffusion layer reaches a constant thickness, for a simple charge transfer reaction. Consequently, the I– E curves obtained under these conditions are SPCs, both for the spherical and planar electrodes. This theoretical prediction is confirmed experimentally for the reversible oxidation of ferrocene in acetonitrile solution of lithium perchlorate, and irreversible reduction of hexaamminecobalt (III) nitrate in aqueous solution of sodium perchlorate.