Effect of anodic treatment on the electrocatalytic activity of electrodeposited Ni-Mo coatings as cathode materials for hydrogen evolution reaction

The influence of anodic treatment of electrodeposited Ni-Mo coatings with different chemical composition, obtained from a self-regulating electrolyte, on the evolution of their morphology and change in roughness parameters was studied. At the same time, the kinetic characteristics of anodic polarization are taken into account, which determine the electrocatalytic activity of the coatings in the hydrogen evolution reaction (HER). The hydrogen evolution reaction on anodized coatings follows the combined Volmer-Heyrovsky mechanism, with the rate determined by the adsorption of hydrogen ions on the coating surface, which correlates with the molybdenum content. The enhanced catalytic properties of the coatings after anodic treatment are attributed to the selective dissolution of nickel, which increases the specific surface area and contributes to the formation of active centers for the electrochemical desorption of hydrogen (molybdenum oxides). The chemical composition and surface morphology of the coatings were investigated using SEM and EDX analyses, while their roughness was assessed by profilometry. Kinetic parameters and the HER mechanism were determined through linear voltammetry and Tafel analysis. The relationships between the kinetic parameters of anodic potentiostatic treatment of Ni-Mo coatings with different compositions in 0.5 M HCl and their surface morphology and roughness coefficients can be used to predict the electrocatalytic activity of materials employed in the electrolytic synthesis of green hydrogen.