Electrochemical reactions on some cemented metal carbides

Abstract

The electrochemical behaviour of cobalt-cemented tungsten carbides has been examined in aqueous alkaline solutions. These electrodes exhibit a good surface stability in the potential region ca. 0.0 – 0.7 V ( vs. RHE); the presence of a passivating surface oxide is indicated in this potential range. The anodic oxidation tendencies of a number of organic compounds were explored but only hydrazine underwent oxidation at an appreciable rate. A detailed mechanistic study on the anodic oxidation of hydrazine has been carried out. The experimental data consist of potentiostatic and potentiodynamic current—potential relationships, reaction order derivatives, apparent heats of activation, and an ellipsometric investigation of the electrode surface. Based on these data and some general considerations, a mechanism is proposed in which the first charge transfer step involving a hydroxyl ion and the molecular residue of hydrazine is the rate-determining step (r.d.s.).