Fig. 1. Illustration of the concepts for designing nano catalysts, SACs and HEA catalysts.

Designed strategies for creating active sites in (a) nano catalysts and (b) SACs. c Schematic illustration of HEA electrocatalysts with identified electronegativity-dependent preferences for active site adsorption of the intermediates OH^* and H^* during H₂O dissociation and H₂ production steps. d Adjustments of the HER activities of HEA electrocatalysts by tailoring the electronegativity of the composition. e Identifying active sites of HEA for stabilization of intermediates by operando electrochemical Raman spectra.