Effect of electrolysis parameters of Ni-Mo alloy on the electrocatalytic activity for hydrogen evaluation and their stability in alkali medium

Abstract

In this paper, NiMo coatings were electrochemically deposited on a copper electrode (Cu/NiMo) and on an electrodeposited nickel onto copper plate (Cu/Ni/NiMo) in citrate solutions. Effects of electrolyte composition, pH value, and temperature on hydrogen-evolution reaction (HER) as well as the electrochemical stability in alkaline solution were investigated, and the electrochemical activation energy was determined for the NiMo alloys. This was evaluated by the determination of kinetic and mechanism of HER in alkali medium by the polarization measurements, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. The morphology and chemical composition of the electrodeposited Ni-Mo were investigated using SEM and EDS analyses. The results showed that the corresponding HER overpotential of the Ni-Mo film depends on alloy composition and surface morphology. As the wt% of Mo content in the alloy is increased, the onset potential of electrode for HER shifted in the positive direction favoring hydrogen generation with lower overpotential. The overall experimental data indicated that the porous Ni-Mo coating on electrodeposited nickel plate was obtained when the molybdenum content was ca. 41 wt%. This electrodes exhibited high catalytic activity in the HER (eta (100) = -48 mV at 100 mA cm(-2) and 80 A degrees C), and their stability was tested by polarization measurements after different anodic and cathodic treatments in 1 M NaOH solution. Moreover, the corrosion behaviors of Ni and Cu/Ni/NiMo electrodes at open-circuit potential were also investigated, and their corrosion resistances were compared.