Designing single-atom catalysts toward improved alkaline hydrogen evolution reaction

Electrochemical water splitting powered by renewables-generated electricity represents a promising approach for green hydrogen production. However, the sluggish kinetics for the hydrogen evolution reaction (HER) under an alkaline medium causes a massive amount of energy losses, hindering large-scale production. Exploring efficient and low-cost catalyst candidates for large-scale H2 generation becomes a crucial demand. Single-atom catalysts (SACs) demonstrate great promise for enabling efficient alkaline HER catalysis at maximum atom utilization efficiency. In this review, we provide a comprehensive overview of the recent progress in SACs for the HER application in alkaline environments. The fundamentals of alkaline HER are first introduced, followed by a justification of the need to develop SACs. The rational design of the SACs including the inherent element property, coordination environment, SAC morphology, and SAC mass loading are highlighted. To facilitate the development of SACs for alkaline HER, we further propose the remaining challenges and perspectives in this research field.