Single‐Atom Catalysts with Microenvironment Tuned by High Entropy for Efficient and Stable Alkaline Hydrogen Evolution Reaction

ABSTRACT Conventional non‐noble hydrogen evolution reaction catalysts are plagued by excessive hydrogen adsorption and instability. To overcome this, we pioneer a high‐entropy single‐atom (HESA) catalyst via precise anchoring of multiple transition metals on carbon supports. The HESA catalyst achieves record‐breaking alkaline HER performance of 44 mV@10 mA cm ⁻² (matching commercial Pt/C catalyst) and 300 h stability, resolving the persistent activity‐stability trade‐off. Systematical characterizations reveal that low‐coordination metal sites induce significant metal‐support charge redistribution. Electronegative supports withdraw electrons from metal centers, while π‐back‐donation downshifts metal d‐band centers, optimizing the Gibbs free energy of intermediate H atoms (ΔG _H* ). Atomic‐scale imaging further confirms uniform charge distribution and Ångström‐level electric field response. Crucially, adjacent multi‐metal sites synergistically lower energy barriers for both water dissociation and hydrogen desorption through a synergistic electronic buffering effect. This work establishes entropy‐driven microenvironment engineering as a paradigm for cooperative optimization of active sites and electronic structures, opening avenues for durable non‐precious catalysts.