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

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.