Kinetics and mechanism of sulphite oxidation on a rotating platinum disc electrode in an alkaline solution

The reaction of sulphite at high pH and room temperature has been examined by cyclic voltammetric methods on a rotating platinum disc electrode. The mechanism of the oxidation reaction is studied by varying the sweep rate, the rotation rate and the concentration. The oxidation of sulphite on a platinum electrode under alkaline conditions appears to follow a catalytic reaction mechanism where weakly adsorbed sulphite is first oxidised to a strongly adsorbed sulphite radical in the rate-determining step. In the next step two sulphite radicals combine and form dithionate, which disproportionate into sulphite and sulphate.