Abstract
Nickel (Ni) alloys are central to next generation electrocatalysts for clean energy conversion, driving key reactions such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and electrochemical CO(2) reduction. Despite extensive performance reports, the mechanistic role of alloying, how it reshapes Ni's structure, electronic states, and surface chemistry to boost activity, remains insufficiently understood. This review moves beyond application-driven summaries to dissect the physicochemical transformations induced by alloying, through d-band modulation, orbital hybridization, and interfacial charge redistribution, and their direct impact on catalytic function. We integrate insights across structural, electronic, and interfacial scales, linking compositional engineering to performance metrics. State-of-the-art synthesis strategies are evaluated, and emerging design principles for durable, high-efficiency Ni-based catalysts are outlined. By uniting mechanistic understanding with material innovation, this work provides a roadmap for accelerating the development of robust, sustainable electrochemical energy systems.