Ni plus Mo composite coatings for hydrogen evolution reaction

Composite Ni + Mo coatings were obtained by electrodeposition of Ni with Mo particles on a steel substrate from the nickel bath in which metallic Mo powder was suspended by stirring. Deposits were characterized by the presence of Mo particles embedded into the crystalline nickel matrix. Incorporation of metallic powder into electrolytic nickel matrix causes an increase in the real surface area of deposits. The composite coatings obtained 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 electrochemical impedance spectroscopy (EIS) measurements. It was ascertained, that Ni + Mo coatings are characterized by enhanced electrochemical activity for this process, which was confirmed by considerable decrease in the hydrogen evolution overpotential at the current density of 100 mA cm(-2) - eta(100), by a nearly 170 - 260 mV compared to nickel electrode. Exchange current density j(0) increases with the increase in Mo content in the coatings. Based on the results of EIS measurements, the rate constants of the HER for Ni and Ni + 44%Mo coatings were determined. The calculated values of surface roughness factor R-f allowed also to evaluate the influence of the real surface area on the electrocatalytic performance of these materials in an alkaline environment. It was stated that the improvement of the electrocatalytic performance of Ni + Mo composite coatings could be attributed to the increase in their real surface area as well as to the synergetic effect of molybdenum with the nickel matrix, as Ni/Mo materials are considered in literature, typical electrocatalysts for the HER. Copyright (c) 2008 John Wiley & Sons, Ltd.