Voltamperometry of a Kinetically Irreversible Electrochemical Process on a Rough Electrode

Abstract

We investigated the role of the effect of morphological inhomogeneity of the electrode surface in the voltammetric response of the irreversible electrochemical process in the mixed-kinetic mode. An algorithm was developed using the Comsol Multiphysics computer package for the numerical simulation of the electrode reaction, including successive stages of irreversible charge transfer and diffusion mass-transfer, using the fi nite element method. By numerical solution of the diffusion-kinetic problem, polarization curves of the irreversible electrochemical process on electrodes with a rough surface formed by the irregularities of various geometric types (sinusoidal surface, surface with protrusions, trapezoidal surface, sawtooth surface, and “random” surface) were obtained. We established the usage conditions for the voltammetric method of studying the kinetics of electrochemical processes under which the roughness of the electrode should be considered. It was found that at relatively high potential scan rates, the voltammetric maximum on the polarization curve was formed under conditions of a very small thickness of the diffusion layer, repeating the profi le of the rough surface, therefore the peak current strength was proportional to the roughness factor. If the scanning rate was relatively low, then by the time the peak on the voltammogram was reached, the diffusion front was completely smoothed out, and the surface roughness of the electrode no longer affected the maximum current. At the same time, the shape of the irregularities responsible for the roughness did not signifi cantly affect the voltammetric response of the irreversible electrochemical process.

Keywords

• voltammetry
• irreversible process
• diffusion