A mechanistic study of Cd(II) reduction at the mercury electrode from aqueous 0.5 M Na2SO4 base electrolyte by the combination of dc and ac voltammetry with the dropping mercury microelectrode technique

Combining the results of three techniques the rate constant k(f) of Cd(II) reduction from aqueous 0.5 M Na2SO4 is obtained in a wide potential range. Just as has been found earlier with other base electrolytes the ln k(f) vs. potential plot is strongly curved, indicating the mechanism of the electrode reaction to consist of several steps. Mathematical analysis of this curve compels us to the conclusion that the mechanism is CEeC. An attempt is made to reconcile the different values of the standard rate constant k(s) and transfer coefficient alpha published over many years, taking into account that experimental data were obtained in different regimes of the electrode potential and often unduly extrapolated to the standard potential. (C) 1997 Elsevier Science S.A.