Non-Precious Electrodes for Practical Alkaline Water Electrolysis

Abstract

Water electrolysis is a promising approach to hydrogen production from renewable energy sources. Alkaline water electrolyzers allow using non-noble and low cost materials. An analysis of common assumptions and experimental conditions (low concentrations, low temperature, low current densities and short-term experiments) found in the literature is reported. The steps to estimate the reaction overpotentials for hydrogen and oxygen reaction are reported and discussed. The results of some of the most investigated electrocatalysts, namely from the iron group elements (iron, nickel and cobalt) and chromium are reported. Past findings and recent progress in the development of efficient anode and cathode materials appropriate for large-scale water electrolysis are presented. The experimental work is done involving the direct-current electrolysis of highly concentrated potassium hydroxide solutions at temperatures between 30 and 100°C which are closer to industrial applications than what usually found in literature. Stable cell components and a good performance was achieved using as a cathode Raney nickel and stainless steel 316L as an anode by means of a monopolar cell at 75°C which ran for one month at 300 mA cm?2. Finally, the proposed catalysts show a total kinetic overpotential of circa 550 mV at 75 °C and 1 A cm?2.