Self-Supported Metallic Alkaline Hydrogen Evolution Electrocatalysts Tolerant for Ampere-Level Current Densities

Electrocatalytic water splitting is an attractive approach for large-scale hydrogen generation, critical for global carbon neutrality. However, the prevalent commercialized alkaline water electrolysis is generally conducted at low current densities due to sluggish kinetics and high overpotential, severely hampering high-efficiency hydrogen production. Exploration of hydrogen evolution reaction (HER) electrocatalysts that can reliably operate at ampere-level current densities under low overpotentials is thus a primary challenge. In contrast to extensive studies using powdery electrocatalysts, the self-supported metallic catalytic cathode has become a burgeoning direction toward ampere-level current densities, owing to their integrated design with intensive interfacial binding, high conductivity and mechanical stability with industrial tolerance/adaption. Recent years have witnessed tremendous research advances in designing self-supported metallic electrocatalysts. Therefore, this flourishing area is specially summarized. Beginning with the introduction to the theory and mechanism of alkaline HER, the engineering strategies on self-supported metallic electrodes are systematically summarized, including metal and alloy construction, heterostructure engineering, doping manipulation, and surface design. Meanwhile, particular emphasis is focused on the relationship between structure, activity, and stability under ampere-level HER. Finally, the existing challenges, requirements of industrial-scale application, and future direction for designing electrocatalysts are summarized, aiming to provide a better solution for industrial alkaline water electrolysis.