High-Entropy Alloy-Induced Triple Synergistic Modulation for Enhanced Electrocatalytic Nitrate Reduction to Ammonia

The electrochemical nitrate reduction reaction (NO₃ ^-RR) provides a promising strategy for sustainable ammonia (NH₃) synthesis. However, achieving efficient NO₃ ^-RR remains a great challenge, primarily due to the kinetic mismatch among NO₃ ^--to-NO₂ ^-, NO₂ ^--to-NH₃, and H₂O dissociation to *H. Here, a multi-site CuCoNiPdAu high-entropy alloy (HEA) catalyst is designed for NO₃ ^-RR, achieving an impressive NH₃ high yield rate of 369.1 mg h^-1 mg_cat ^-1 with a corresponding NH₃ Faraday efficiency of 93.2% at -0.4 V vs.  reversible hydrogen electrode, exceeding most of the electrocatalysts reported recently. Moreover, a Zn-NO₃ ^- battery assembled with this HEA as the cathode delivers a remarkable power density of 7.37 mW cm^-2 and an NH₃ yield rate of 2.0 mg h^-1 cm^-2, enabling simultaneous electricity generation and NH₃ production. Experimental and theoretical results demonstrate that the multi-site feature of the CuCoNiPdAu HEA surface induces triple synergistic modulation toward boosting the NO₃ ^-RR performance: Cu-Ni sites promote the conversion of NO₃ ^- to *NO₂, Co-based sites facilitate the transformation of *NO₂ to NH₃, and Ni sites accelerate the dissociation of H₂O to supply abundant *H. This study provides valuable insights for the rational design of HEAs with multiple active sites tailored for multi-step reactions.