Synergistic Dual Sites and Hydrogen Spillover Enable Efficient Ammonia Synthesis From Electrochemical Nitrate Reduction

ABSTRACT The efficient synthesis of ammonia via electrochemical nitrate reduction (eNO 3 RR) hinges critically on the generation, migration, and utilization of active hydrogen species (*H), whose fundamental mechanisms, however, remain ambiguous. Herein, a ternary CuO/NiO/Ni 4 N heterojunction featuring dual Ni sites and a Cu site was constructed. This catalyst significantly enhances eNO 3 RR performance by promoting the overflow of abundant *H from the dual Ni sites to the Cu site. Specifically, the Cu site facilitates NO 3 − adsorption and reduction to NO 2 − , while the Ni sites efficiently dissociate water to generate *H, which rapidly migrates to the adjacent Cu site for subsequent deoxygenation and hydrogenation. This synergistic process accelerates the reaction kinetics and improves overall catalytic efficiency. Consequently, at −0.8 V versus RHE, the CuO/NiO/Ni 4 N catalyst achieves an exceptional ammonia production rate of 22,400 µg h −1 cm −2 with a Faradaic efficiency of 96.7%. Notably, it also exhibits remarkable stability, maintaining consistent performance over 230 h of continuous operation even at a high current density of 540 mA cm −2 . When employed as a cathode in a zinc‐nitrate battery, the catalyst further demonstrates excellent performance. This work presents a rationally engineered heterojunction that drives efficient ammonia synthesis through a hydrogen spillover pathway, providing valuable insights for eNO 3 RR.