The hydrogen evolution reaction (HER) is the cathodic half-reaction of water electrolysers for producing hydrogen (H2) gas in a carbon-neutral manner. In the pursuit of system-level H2 production under less corrosive conditions, an alkaline water electrolyser provides a promising means of energy conversion. However, the sluggish kinetics of the alkaline HER, originating from an additional water dissociation step required for surface hydrogen adsorption, remains an important challenge. The complex nature of the alkaline HER mechanism renders the identification of an all-embracing activity descriptor a current topic of debate, which in turn hinders the design of high-performance catalysts for the alkaline HER. In this review, we present recent attempts to reach a consensus on the activity descriptors of the alkaline HER. We summarise activity-descriptor-guided design strategies for high-performance nanocatalytic materials for the alkaline HER with notable examples. We have tabulated activity parameters of representative catalysts. We conclude this review by suggesting future perspectives gleaned from this study.
