Triggering Intrinsic Electrochemical Hydrogen Evolution Activity within Heusler Alloys via Electronegativity‐Induced Charge Rearrangement

Abstract Heusler alloys have gradually attracted extensive research interests in the electrochemical hydrogen evolution reaction (HER) due to their unique structural features. However, the inherent half‐metallic characteristics of them impede their application. Therefore, reasonable tuning the electronic structure of Heusler alloy catalysts is crucial for enhancing their catalytic activity. Here, we modulated the Fe 2 MnSi Heusler alloy by precisely substituting Mn with Ru using arc melting and prepared Fe 2 Mn x Ru 1‐ x Si materials with enhanced HER properties. The incorporation of highly electronegative Ru introduces substantial electronegativity gradients among the metals, prompting a pronounced Ru‐induced electron enrichment effect that facilitates significant charge redistribution. This electronic modulation enhances conductivity and fine‐tunes the d‐band center, ultimately optimizing the hydrogen adsorption energy barrier at the Si active site. As a result, the overpotential at a current density of 10 mA cm −2 is significantly reduced from 525 mV to 19 mV under acidic conditions. This work provides insights into the design of highly efficient HER electrocatalysts and expands the potential applications of Heusler alloys in electrocatalysis.