Monometallic Nickel as a Tunable Electrocatalyst for Alkaline Hydrogen Evolution: A Critical Review

Abstract

The hydrogen evolution reaction (HER) is a cornerstone of water electrolysis technologies for sustainable hydrogen production. Nickel-based catalysts have emerged as leading non-precious alternatives to platinum due to their abundance, electrochemical stability in alkaline environments, and tunable physicochemical properties. This review critically examines recent advances in the synthesis, surface/interface modification, and performance optimization of monometallic Ni HER electrodes, emphasizing how rational engineering can elevate their reactivity toward state-of-theart levels. A comprehensive overview of fabrication techniques, including electrodeposition, hydrothermal synthesis, pulsed laser deposition (PLD), physical vapor deposition (PVD), laser nanomachining, and chemical vapor deposition (CVD), is presented with a focus on how these methods tailor microstructure, active-site density, and interfacial chemistry. Special attention is given to engineering strategies such as defect induction (e.g., oxygen vacancies), interface engineering, and hierarchical nanostructuring, which regulate surface reactivity, charge-transfer behavior, and catalytic efficiency. Across the literature, these approaches have produced monometallic Ni electrodes with overpotentials as low as ~ 40-50 mV at 10 mA cm -2 , and Tafel slopes in the range of 55-65 mV dec -1 , values that approach or, in some cases, rival those of multicomponent Ni-based electrocatalysts (e.g., Ni-Mo, Ni-Fe) and significantly narrow the performance gap to Pt-group materials under alkaline conditions. By systematically correlating synthesis routes, structural descriptors, and HER metrics, this review demonstrates how monometallic Ni can achieve high intrinsic activity, robust durability, and industrially relevant current densities without relying on noble metals or complex alloying. Furthermore, by outlining a strategic roadmap to translate these lab-scale advances into scalable manufacturing processes, these insights establish monometallic nickel not only as a benchmark model system for mechanistic studies but also as a technologically viable catalyst platform for next-generation alkaline hydrogen production.