Engineering Asymmetric Cu ⁰ /Cu ⁺ Interfaces for Record‐Efficiency Ammonia Electrosynthesis From Dilute Nitrate in Neutral Media

ABSTRACT The electrocatalytic conversion of nitrate to ammonia in neutral media offers profound potential for sustainable nitrogen management, albeit it has been critically impeded by persistent hurdles such as the sluggish kinetics and competitive adsorption of H ₂ O molecules. Herein, we report the reconstruction of copper foam to engineer asymmetric Cu ⁰ /Cu ⁺ interfaces for electrocatalytic nitrate to ammonia conversion in neutral conditions with ultralow nitrate concentration. Employing microstructural characterizations complemented by kinetic isotope effect (KIE) analyses, we uncover that the Cu ₂ O/Cu foam electrocatalyst fosters the formation of asymmetric rectifying interfaces, thereby facilitating nitrate adsorption and accelerating the hydrogenation of H‐ON in neutral environments. Notably, under conditions of ultralow nitrate concentration (14 ppm NO ₃ ⁻ ‐N), the Cu ₂ O/Cu foam electrocatalyst demonstrates a remarkable 100% conversion of NO ₃ ⁻ to NH ₃ within 15 min, with a NO ₃ ⁻ removal ratio of 99.9% and an NH ₃ production rate of 0.39 mmol/h/cm ² , effectively diminishing nitrate levels to adhere to the WHO safety limit.