Production and electrochemical characterization of Ni-based composite coatings containing titanium, vanadium or molybdenum powders

Composite Ni + Ti, Ni + V and Ni + Mo coatings were prepared by codeposition of Ti, V or Mo particles in an Ni matrix on a carbon steel substrate from the nickel bath in which metallic powder was held in suspension. The influence of the metal powder amount in the bath, as well as the deposition current density on chemical composition of obtained coatings has been investigated. It was stated that the content of incorporated Ti, V and Mo increases with the increase in the particle concentration in the electrolyte, and diminishes with the increase in the deposition current density. The mechanism of metallic particles embedding was explained on the base of Ni2+ ions adsorption process. Deposits exhibited a presence of Ti, V or Mo microsize particles embedded into the nanocrystalline nickel matrix. Incorporation of metallic powder into electrolytic nickel matrix results in the significant increase in the real surface area of the deposits. Electrodeposited composite coatings were tested as electrode materials for hydrogen evolution reaction (HER) in an alkaline environment. Electrochemical characterization was carried out by steady-state polarization method. All composite materials showed enhanced electrochemical activity for HER compared to the nickel electrode. Based on determined values of exchange current density-j0 and the values of hydrogen evolution overpotential at 100 mA cm− 2-η100 the variation in the electrochemical activity of Ni + Ti, Ni + V and Ni + Mo composites in dependence on their chemical composition and the kind of incorporated component was evaluated. Comparison of the investigated materials leads to the statement that the highest activity towards the HER exhibit Ni + Mo deposits.