Heterophase fcc‐hcp‐fcc High‐Entropy Alloy Nanomaterials with Tailored Electron Divergence for Selective Ammonia Electrosynthesis

ABSTRACT Electrocatalytic nitrate reduction reaction provides a broad prospect for developing green electrochemical ammonia production and efficient treatment of industrial wastewater rich in nitrate, but poses a challenge to the high activity and stability of electrocatalysts. Herein, we report the versatile and scalable one‐pot solvothermal synthesis of a series of RuFeMMnMo (M═CoNi, Co, and Ni) high‐entropy alloy (HEA) nanomaterials, possessing a unique face‐centered cubic‐hexagonal close‐packed‐face‐centered cubic ( fcc‐hcp‐fcc ) heterophase. The highly random distribution of multiple metal components and the tunable diversity of metal atomic arrangements can be realized simultaneously. Significantly, RuFeCoNiMnMo HEAs present a high Faradaic efficiency of 99.3 % and a promising yield rate of 83.35 mg h −1 mg cat −1 toward ammonia production at −0.6 V vs. reversible hydrogen electrode. Ex/in situ characterizations and theoretical calculations have revealed that by high electron coupling of high‐entropy effect, heterophase fcc‐hcp‐fcc RuFeCoNiMnMo HEAs have shown strong electronic modulations with charge redistributions. The positive charges and negative charges for Ru sites and Ni/Co sites promote the adsorption of key intermediates and generation of active protons, respectively, which guarantees efficient nitrate reduction due to the reduced energy barriers.