The kinetics of electroreduction of peroxodisulfate anion on electrochemically polished Cd(0 0 0 1) plane

Abstract

The electroreduction of the peroxodisulfate anion on the electrochemically polished (EP) Cd(0 0 0 1) plane has been studied by cyclic voltammetry and rotating disc electrode methods. The rate constant of the heterogeneous electroreduction reaction of the S 2O 8 2− anion on the EP Cd(0 0 0 1) plane dependent on electrode polarisation and base electrolyte concentration has been established. The values of apparent transfer coefficient α app corrected for the double layer effect, noticeably lower than 0.5 for the EP Cd(0 0 0 1) plane, only very weakly depend on the electrode potential but noticeably on the electrolyte concentration, decreasing with the base electrolyte concentration. The very low values of the apparent charge transfer coefficient show that the activationless charge transfer mechanism is probably valid for EP Cd(0 0 0 1) | NaF+ Na 2 S 2 O 8 aqueous solution interface in a good agreement with the theoretical models for the high hydrogen overvoltage metals based on the diabatic charge transfer mechanism from the metal to an ion.