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Abstract

A theoretical and experimental investigation is presented for mass transfer to a rotating hemispherical electrode when direct current (DC) superimposed with symmetrical triangular- or square-wave alternating current (AC) is used for electrolysis. A film model is used for the analysis of AC concentration components. The limiting AC current density corresponding to a zero instantaneous surface concentration and the phase shift between the applied AC and the periodic potential changes are calculated and compared to the experimental studies. The experimental data agreed with the theoretical prediction to within ±8% in the regime of a dimensionless AC frequency K = (ω/Ω)Sc1/3 greater than 1 and less than 180. The mass transfer behavior with the triangular and square waves is further compared to that of the sinusoidal current. It is found that for a given AC frequency and rotational speed, the limiting AC current density on the electrode decreases in the order of traingular-wave AC > sinusoidal AC > square-wave AC.