Mathematical model for evaluating permeability and electrode reversibility in thin-film voltammetry. Part 2: Cyclic voltammetric behavior

Abstract

This manuscript presents a general mathematical solution for describing profiles of staircase cyclic voltammetry (SCV) where the diffusion of electroactive species occurs into thin-film (TF) materials of different permeability. The TF material can involve a film of a solid, a liquid, or a mixture of both. However, for simplicity, the model focuses on a system conformed by an external aqueous solution in contact with a thin organic film that covers the electrode surface. Thus, the partition of the electroactive species takes place between the aqueous and organic phases while the charge transfer reaction occurs at the electrode.The variation of scan rate in SCV affects the apparent thickness and reversibility of the system, which complicates the behavior expected for the peak current and peak potential. It is advisable to study the system using both chronoamperometry and SCV since the first can be used to estimate the partition and the second to evaluate the other relevant parameters. This manuscript shows how to use the dependencies of peak currents and peak potentials on the scan rate to estimate the thickness and charge transfer rate values of a TF system.