Cu‐Enhanced Sigma Phase High‐Entropy Intermetallics Enabling Efficient Hydrogen Evolution Through Hydrogen Spillover

ABSTRACT High‐entropy intermetallics (HEIs) exhibit outstanding stability in alkaline water electrolysis, but their application as catalysts is strictly restricted by sluggish hydrogen evolution reaction (HER) kinetics. Hydrogen spillover offers a promising strategy to address this challenge, enabling timely replenishment of active hydrogen in alkaline media through migration from water dissociation sites to adjacent catalytic domains. Herein, we report a Sigma phase HEIs catalyst S‐MnFeCoNiVCu, where spillover carrier‐Cu incorporation into the high‐entropy topological close‐packed structure significantly enhances hydrogen spillover efficiency. This catalyst exhibits excellent HER performance in 1 m KOH, requiring only 161 and 266 mV to achieve current densities of 100 mA cm −2 and 500 mA cm −2 , respectively. The markedly reduced Tafel slope (46.93 mV dec −1 ) and enhanced hydrogen adsorption/desorption kinetics provide clear evidence of hydrogen spillover phenomena during HER. The inherent structural stability of Sigma phase HEIs ensures ultra‐durable operation over 6000 h at 500 mA cm −2 with no detectable degradation. This work demonstrates a novel catalyst design paradigm through synergistic structural engineering and spillover carrier element incorporation, offering fresh insights into hydrogen spillover‐enhanced alkaline HER.