The influence of diffusion coefficients in a catalytic electron transfer mechanism on linear sweep voltammetric and potential step chronoamperometric measurements

Abstract

The kinetic equations for a catalytic mechanism consisting of a homogeneous electron transfer followed by two competing fast second-order reactions, a coupling reaction and a homogeneous electron transfer, are solved by digital simulation for linear sweep voltammetry and potential step chronoamperometry at a stationary planar electrode. The simulations allow determination of the first homogeneous electron transfer rate constant kET and a competition parameter q for the two follow-up reactions. The influence on the current of different ratios of the diffusion coefficients of the species involved was examined and it is shown that it can be rationalized from a combined “near-reversible”, steady-state and “total catalysis” approach. The lack of consideration of unequal diffusion coefficients may introduce errors in the experimental determination of the parameter q.