Phase Engineering of High‐Entropy Alloy for Enhanced Electrocatalytic Nitrate Reduction to Ammonia

Abstract

Directly electrochemical conversion of nitrate (NO₃ ^-) is an efficient and environmentally friendly technology for ammonia (NH₃) production but is challenged by highly selective electrocatalysts. High-entropy alloys (HEAs) with unique properties are attractive materials in catalysis, particularly for multi-step reactions. Herein, we first reported the application of HEA (FeCoNiAlTi) for electrocatalytic NO₃ ^- reduction to NH₃ (NRA). The bulk HEA is active for NRA but limited by the unsatisfied NH₃ yield of 0.36 mg h^-1 cm^-2 and Faradaic efficiency (FE) of 82.66 %. Through an effective phase engineering strategy, uniform intermetallic nanoparticles are introduced on the bulk HEA to increase electrochemical active surface area and charge transfer efficiency. The resulting nanostructured HEA (n-HEA) delivers enhanced electrochemical NRA performance in terms of NH₃ yield (0.52 mg h^-1 cm^-2) and FE (95.23 %). Further experimental and theoretical investigations reveal that the multi-active sites (Fe, Co, and Ni) dominated electrocatalysis for NRA over the n-HEA. Notably, the typical Co sites exhibit the lowest energy barrier for NRA with *NH₂ to *NH₃as the rate-determining step.