Hydrogen evolving activity on nickel–molybdenum deposits using experimental strategies

Hydrogen evolution on various Ni–Mo deposits was systematically compared using fractional factorial design (FFD) and response surface methodology (RSM). The electroplating variables such as pH, Ni/Mo atomic ratio and citrate concentration were found to be the key factors affecting the hydrogen evolution activity from the FFD study. The effects of Ni/Mo atomic ratio and citrate concentration in the plating bath on the apparent current density, the exchange current density, and the specific activity (based on i/q*) of hydrogen gas evolution, and on the Mo/(Ni + Mo) ratio of the deposits were examined using regression models. These models, represented as response surface contour plots, showed the maximum hydrogen evolving activity occurring on the Ni–Mo deposit electroplated from the bath with a pH of 8, a Ni/Mo ratio of 3.3 and a citrate concentration of 40 g l−1, respectively.