Non-stationary processes at polymer coated rotating disk electrodes. Part I. Model and simulation

A time dependent model for the mediated oxidation of a substrate in bulk solution at a polymer modified rotating disk electrode is proposed and a numerical solution is found by orthogonal collocation. The mediation system consists of a surface bound redox species which can accept electrons from a substrate in solution. In the model considered here the substrate can enter the film freely but does not react at the electrode surface. The effect of the variation of substrate concentration, mediator concentration, effective charge transfer diffusion coefficient of the bound species and homogeneous rate constant on the electrochemical behaviour of the modified electrode is considered. Good qualitative agreement was found between simulated current-potential curves and experimental curves using [Fe(CN)₆]^4- a substrate and [Ru(bpy)₂Cl(PVP)₅]Cl as the polymer coating.