Surface concentration nonuniformities resulting from chronoamperometry of a reversible reaction at an ultramicrodisk electrode

•Accurate numerical simulations of chronoamperometry at an UMDE.•Effect of unequal diffusion coefficients of the redox couple is evaluated.•Nonuniformities of surface concentrations over the disk are observed.

The chronoamperometric experiment at a disk electrode was simulated, assuming a reversible reaction. When the diffusion coefficients of the two substances involved are different, there appears a surface concentration nonuniformity in the radial direction, exhibiting a maximum effect in time. At long times, the nonuniformity disappears.