Mass transfer in AC electrolysis part I: Theoretical analysis using a film model for sinusoidal current on a rotating hemispherical electrode

Abstract

AbstractA film model is presented for the analysis of mass transfer to a rotating hemispherical electrode when sinusoidal alternating current (AC) together with direct current (DC) are flowing across the electrode surface. The concentration of a diffusing ion is separated into two independent components: a constant DC component and a periodic AC component. The DC concentration is obtained by solving the steady‐state convective mass transport equation with the perturbation method. The periodic AC concentration distribution is analyzed by the solution to the one‐dimensional transient diffusion equation based on the concept of Nernst diffusion layer. The limiting AC current densities corresponding to a zero surface concentration of a reactive ion are investigated for various DC current densities and AC frequencies. The resulting periodic concentration overpotential wave and its phase shift with respect to the applied AC are examined. A comparison with a previous rigorous model indicates that the film model is a good approximation to the mass transfer calculation in the regimes of a dimensionless AC frequency K = (ω/Ω)Sc1/3 greater than 2 and less than 0.01.