Revestimentos de Ni-Mo obtidos em meio de solvente eutético como eletrocatalisador na reação de desprendimento de hidrogênio

Abstract

The hydrogen has been presented as an alternative to the consolidated use of fossil fuels, due to high energy efficiency, and consumption free of carbon dioxide. However, obtaining clean hydrogen is still a challenge, since the electrolysis of water demands a high energy cost and requires electrocatalysts that can reduce this cost. The most efficient electrocatalysts are prepared from noble metals, such as platinum and palladium, but the scarcity of these materials and their high cost make them unviable for use on a large scale, requiring the development of electrocatalysts with similar efficiency from metals abundant, such as Fe, Ni and Co. Thus, the objective of this work is to develop Ni-Mo coatings in eutectic mixture on a copper surface and to evaluate electrocatalytic activity in the hydrogen evolution reaction. Cyclic voltammetry tests were carried out for the electrochemical investigation of the ionic species of nickel and molybdenum in a 16:1 molar ratio in eutectic mixture, identifying processes of reduction of metallic cations at ₋0.95 V, at 298 K, and at ₋1.0 V versus Ag/AgCl/DES, at 343 K. Ni-Mo coatings were obtained by chronoamperometry with load control for a theoretical thickness of 4µm, and showed granular morphology with cracks on its surface, influenced by temperature of electrodeposition. Linear scanning voltammetry and electrochemical impedance spectroscopy tests indicated that Ni-Mo coatings have the Volmer step as a determining step in the mechanism of the hydrogen evolution reaction, and that they have high electrocatalytic efficiency, compared to commercial copper, 1020 carbon steel and Ni coatings, thus being the ideal coating for reducing energy costs in hydrogen production.