Electrochemical and photoelectrochemical reduction of oxygen at semiconductor electrodes in molten amides

Abstract

Dissolved oxygen reduction has been studied at the layered semiconductors n-MoSe₂, n-WSe₂ and p-MoSe₂ and also at a pyrite (n-FeS₂) semiconductor in molten acetamide (85°C) and in an amide mixture of acetamide + urea + ammonium nitrate (25-85°C). The reduction is found to be a single-step irreversible two-electron diffusion-limited process under both dark and illuminated conditions. Quasimetallic behaviour is inferred at the n-type electrodes, while large band bending is inferred at the p-type electrodes. Illumination shifts the reduction peak potentials at a p-MoSe₂ electrode by + 0.5 V and increases the peak currents by 40% at all the temperatures studied. The hydrogen peroxide formed decomposes at temperatures above 50°C; the decomposition kinetics are analysed.