Non-noble metal catalysts for the alkaline hydrogen evolution reaction: a review

Electrochemical hydrogen production in alkaline media faces distinct mechanistic challenges compared with acidic conditions, largely due to the extra water dissociation step (Volmer reaction) and slower hydrogen adsorption and desorption kinetics. Non-noble electrocatalysts have attracted significant attention as cost-effective alternatives to platinum, offering a balance between activity, stability, and scalability using earth-abundant elements. This review provides a comprehensive overview of non-noble alkaline HER catalysts, spanning transition metal oxides and hydroxides, layered double hydroxides (LDHs), transition metal phosphides, nitrides, borides, MOF-derived materials, single- and dual-atom catalysts, MXene-based hybrids, boron-rich metal-free frameworks, and advanced 1D/2D architectures. Emphasis is placed on the evolving nature of catalyst surfaces, highlighting phenomena such as in situ reconstruction and the pre-catalyst concept, which often dictate the true active sites under reaction conditions. We examine how intrinsic catalytic kinetics, electron and mass transport, structural durability, and high-current operation interact, and highlight strategies such as heterostructure engineering, hierarchical design, doping, and integration with conductive scaffolds. By combining fundamental understanding with practical electrode considerations, this review outlines the principles necessary for designing alkaline HER catalysts that are both efficient and durable, moving closer to practical water electrolysis applications.