Isolated Copper Atoms Boost *NO3 Adsorption and Active Hydrogen Retention over Zinc Oxide for Ammonia Electrosynthesis at Ampere-Level Current Densities

Abstract

The use of renewable electricity to drive the electroreduction of nitrate to ammonia can simultaneously achieve the green synthesis of ammonia and alleviate the environmental pollution of nitrate. However, the industrial requirement for ammonia synthesis with ampere-level current densities remains a grand challenge. In addition, the electroreduction of nitrate to ammonia reaction requires multiple steps of deoxygenation and hydrogenation of *NO₃ intermediates. Therefore, it is urgent to clarify the relationship between the adsorption strength of *NO₃/*H (active hydrogen) intermediates and the catalytic activity. Herein, we achieved highly selective ammonia electrosynthesis at ampere-level current densities by anchoring atomically dispersed copper atoms on zinc oxide (ZnO) nanospheres (Cu₁/ZnO). The synthesized Cu₁/ZnO delivers a high NH₃ yield rate of 184.7 mg h^–1 cm^–2 with an NH₃ Faradaic efficiency of 96.1% and an NH₃ partial current density of 2.23 A cm^–2 in a flow cell. Based on mechanistic studies, anchoring Cu single atoms over ZnO enhances the adsorption of the *NO₃ intermediate and the retention of *H generated by water dissociation, resulting in the decreased energy barrier of the rate-determining step of *NO-to-*NHO.