A Model for a Redox Species Confined to a Thin Layer with a Variable Diffusion Coefficient

A numerical simulation has been carried out for a redox couple confined to a thin layer under potential step or cyclic voltammetric conditions where the diffusion coefficient is determined by the relative amounts of the oxidized form (of diffusion coefficient D₁) and reduced form (of diffusion coefficient D₂). An overall layer diffusion coefficient D is determined by the mole fractions of species 1 and 2; D(n₁ + n₂) = n₁D₁ + n₂D₂. This layer diffusion coefficient is proposed as an alternative model to that of interaction parameters used to characterize nonidealities during potential step and cyclic voltammetric experiments of surface confined redox species.