Hydrogen evolution reaction on smooth tungsten carbide electrodes

Abstract

The open-circuit potential in H 2-saturated electrolytes, and the kinetics of hydrogen reactions, in particular of hydrogen evolution reaction, on smooth, rotating disc tungsten carbide WC electrode have been investigated, in 0.5 M sulfate solutions of pH 0.3 and 1.85, in the temperature range 30 to 80°C. Anodically activated electrodes were used too. It was proved that values of the open-circuit potential in the near vicinity of reversible hydrogen electrode potential can be observed, under condition of high purity, and of tight mounting of the sample in the electrode holder. Two Tafel regions have been observed for hydrogen evolution reaction, both the Tafel slopes having no systematic variation with temperature. In the lower overpotential region the experimental charge transfer coefficient attained the value of 1, when the temperature was increased up to 80°C. It was suggested that the process approached the barrierless form when the temperature was increased. The mechanism of hydrogen reactions on WC was discussed. It was suggested that the rate of the process is possibly determined by the rates of its two steps simultaneously. The role of pH on the activation process of WC was emphasized, and implications of the hydrogen evolution reaction parameters on the mechanism of this process were pointed out.