Numerical investigation of transient current density distributions for multi-ion electrolytes at a rotating disk electrode.

A versatile model for the simulation of transient multiion transport and reaction processes is applied to investigate current density distributions over a rotating disk electrode for linear voltammetric sweep experiments. The model accounts for ion transport by convection, diffusion, and migration, in combination with Butler-Volmer type electrode reactions. For several process conditions (reversible and irreversible reactions, excess or lack of supporting electrolyte), the current density distribution over the disk surface is examined and the transient current response is compared to results from the more commonly used one-dimensional axial approach. The impact of migrational effects on the nonuniform local process conditions over the disk surface is illustrated, and the resulting effect on the current peak height, width, and position is investigated. A mathematical correlation for the current peak height as a function of the reacting ion transference number is established.