Alloying Ni4Mo for efficient alkaline hydrogen oxidation and hydrogen evolution reactions

Abstract

Developing low-cost transition metal electrocatalysts to substitute advanced noble metals is significant for hydrogen electrocatalysis, including hydrogen oxidation (HOR) and hydrogen evolution (HER) reactions. Ni-based materials exhibit a high potential for application in the hydroxylation and hydrogen evolution reactions in alkaline media due to their superior electrocatalytic properties. Nevertheless, their commercial utilization is often constrained by insufficient activity. Herein, we report alloying Ni₄Mo nanoparticles grown on reduced oxide graphite as a bifunctional electrocatalyst. In an alkaline electrolyte, it exhibits a current density of 1.63 mA cm⁻² at an overpotential of 100 mV for the HOR, and an overpotential of 51 mV at 10 mA cm⁻² for the HER, surpassing those of the commercial 20 wt% Pt/C catalyst. The anion exchange membrane fuel cell assembled using Ni₄Mo/rGO as the anode reaches a high peak power density of 369 mW cm⁻² at a voltage of 0.5 V, and it shows superior durability for 35 h. DFT calculations indicate that alloying Ni₄Mo could enhance H* as well as OH* adsorption, improving both HER and HOR activity. The present work provides an effective strategy for optimizing catalyst activity, which is of great significance for the development of efficient and low-cost HOR/HER catalysts.