Electrode materials for hydrogen energetics

Abstract

The electrodeposition of molybdenum, tungsten and zirconium alloys with cobalt from biligand electrolytes by pulsed-current made it possible to obtain composite coatings with a unique combination of physicochemical properties unattainable when using other application methods. In addition to the composition of the composite electrolytic coatings obtained, the catalytic evolution of hydrogen is influenced by the characteristics of their surface, in particular the relief and morphology. Surface topography was studied using a scanning atomic force microscope by the contact method. Comparison of the deposited coatings surface topography shows that the most uniformly developed and microglobular are composites of the composition Co-Mo-WOx and Co-Mo-ZrO2. The electrolytic reaction of hydrogen evolution is a multi-stage process, so to determine the catalytic activity of cobalt-based composite coatings, it is necessary to determine the mechanism by which this process occurs. The evaluation of the electrocatalytic properties of composite coatings based on cobalt alloys of different composition was performed on the basis of the analysis of kinetic parameters of the model reaction of hydrogen evolution from electrolytes of different acidity. Tafel constants, transfer coefficients, exchange current density for the electrochemical hydrogen evolution reaction on composite electrolytic coatings was determined. According to the magnitude of the exchange current of the electrochemical reaction of hydrogen evolution on the Co-Mo-WOx, Co-Mo-ZrO2, Co-W-ZrO2 coatings, their high electrocatalytic activity compared to individual metals and binary alloys was established. It is shown that the electro-reduction of hydrogen on composite cobalt alloys proceeds by the Volmer-Tafel mechanism with a slow recombination stage. Schemes of the reactions by which the reduction of hydrogen proceeds, if the intermediate of the common process are metal hydrides, are proposed.