KINETICS OF CHLORINE ELECTRODE REACTION AT A PLATINUM ELECTRODE

The formation and reduction of chlorine at a platinum electrode are both inhibited by the oxide which is formed on the electrode surface. Current/potential curves for the reduction process have been obtained at an electrode with a constant oxide-coverage at different chlorine concentrations and oxide-coverages. In 1 M HCl solution the reaction order with respect to chlorine is 1 at low chlorine concentrations but falls with increasing concentration. A nonlinear relation between the electrode potential and log i is observed even at appreciable overpotentials. The simplest mechanism in accord with these results is. Cl2(aq) + M + e ⇌ ClM + Cl-(aq). ClM + e → M + Cl-(aq), in which the last step is rate determining, but comparable in rate to the reverse of the first step. As the amount of oxide on the electrode is increased, the rate of the reduction process decreases and the transfer coefficient first decreases and then remains constant. There is no evidence for a change in mechanism. © 1969.