Electrolytic Ni-based composite coatings containing molybdenum and silicon for hydrogen evolution reaction

Abstract

Ni + Mo + SiNi composite coatings were prepared by codeposition of Ni with powders of molybdenum and silicon (covered with the electroless plated nickel – SiNi) on a steel substrate from the nickel bath in which Mo and SiNi particles were suspended by stirring. Deposition was conducted under galvanostatic conditions. Deposits were characterized by the presence of Mo and Si phases embedded into the nickel matrix. For comparison Ni + Mo composite coatings without silicon were obtained under comparable conditions. Incorporation of Mo and SiNi powders into electrolytic nickel matrix causes an increase in the real surface area of the deposits. The obtained composite coatings were tested as electrode materials for hydrogen evolution reaction (HER) in an alkaline environment. Electrochemical characterization of the composites was carried out by steady-state polarization method and EIS measurements. It was ascertained, that Ni + Mo + SiNi coatings are characterized by enhanced electrochemical activity for this process which was confirmed by considerable decrease in the hydrogen evolution overpotential compared to nickel electrode as well as to the Ni + Mo composite coatings. Basing on the results of EIS measurements the rate constants of the HER were determined. The calculated values of surface roughness factor allowed to study the apparent and intrinsic activity of investigated coatings for the HER. It was stated that the improvement of the electrocatalytic performance of Ni + Mo and Ni + Mo + SiNi composite coatings could be attributed both to the increase in their real surface area as well as to the synergetic effect of molybdenum with the nickel matrix.