Nickel-Based Catalysts for Hydrogen Evolution Reaction (HER) in Alkaline Medium

Abstract

The hydrogen evolution reaction (HER) in alkaline media is a key half-reaction for sustainable electrochemical water splitting, yet its practical efficiency is limited by sluggish kinetics arising from the additional water dissociation (Volmer) step. Developing cost-effective and high-performance non-precious metal electrocatalysts is therefore essential for large-scale hydrogen production. Among various candidates, nickel-based materials have attracted considerable attention due to their abundance,stability in alkaline environments, and tunable electronic structure; however, their intrinsic activity remains insufficient for industrial requirements. In this work, a systematic and directly comparable study of nickel-based electrocatalysts,including Ni-Mo alloy,and MOF-derived Ni/N-doped carbon, is presented to establish clear structure-activity relationships for alkaline HER. The Ni-Mo catalyst exhibits the highest activity, delivering an overpotential of 68 mV at 10 mA cm-2, a Tafel slope of 34 mV dec-1, and the lowest charge-transfer resistance (1.4 Ω), outperformingNi2P, MOF-derived Ni,NiO, and Ni(OH)2. This superior performance is attributed to synergistic bifunctional catalysis, where Mo sites facilitate water dissociation while Ni sites optimize hydrogen adsorption and recombination kinetics. Mechanistic analysis confirms that the Volmer step is the rate-determining process in alkaline media, and catalytic enhancement is governed by the optimization of hydrogen adsorption free energy (ΔG_H*), improved interfacial electron transfer, and increased active site exposure. Structural and electronic characterization further reveals that alloy formation, phosphidation, and carbon confinement effectively tune the electronic structure of nickel, thereby accelerating HER kinetics. Overall, this study provides a unified comparison of Ni-based catalytic systems and demonstrates that electronic modulation through Ni-Mo alloying is the most effective strategy for achieving high-performance alkaline HER. These findings offer valuable design principles for the development of efficient and scalable non-precious metal electro catalysts for hydrogen energy applications.