The electrocatalysis in hydrogen evolution reaction (HER) is critical to improve the technology of hydrogen production from water electrolysis. The electrochemical codeposition process of particles and metallic ions has significant advantages in obtaining high-performance HER electrocatalysts, which can be employed to achieve large surface areas and synergetic effects of the particles and metallic ions for the electrocatalysts.

In this work, AB5-type mischmetal-based hydrogen storage alloys were codeposited with nickel to prepare Ni-AB5 composite electrodes. The morphology of the pure-Ni and Ni-AB5 electrodeposits was examined with SEM. The electrocatalytic characteristics of Ni-AB5 electrodes for HER in 28 wt.% KOH were investigated by steady-state polarization curves and electrochemical impedance spectroscopy (EIS). The results showed that in comparison with those of pure-Ni electrodes, Ni-AB5 electrodes exhibited a lower overpotential and higher exchange current density for HER, suggesting a higher electrocatalytic activity. The standard activation free enthalpy of HER was measured through polarization curves, which was found to be 74.2 and 39.8 kJ/mol for pure-Ni and Ni-AB5 electrodes, respectively. As revealed by SEM and EIS, Ni-AB5 electrodes also possessed a higher surface area and lower electrochemical reaction impedance. Accordingly, superior electrocatalytic properties could be obtained for Ni-AB5 electrodes as related to pure-Ni electrodes. The mechanismic study suggested that the main pathway for HER on Ni-AB5 electrodes in alkaline solutions was Volmer-Heyrovsky with the electrochemical desorption (Heyrovsky reaction) as the rate-determining step. Thus, Ni-AB5 composite electrodes prepared by electrodeposition were very promising for use in the electrochemical production of hydrogen from water electrolysis.