Electrochemical nitrate reduction to ammonia (NRA) is an emerging sustainable technology that converts nitrate contamination in wastewater into the value-added chemical ammonia. Copper-based catalysts represent one of the most competitive non-noble NRA electrocatalysts due to their robust nitrate adsorption capability. In this study, we developed a series of Bi-Cu bimetallic oxides (BiCuOx) with mixed oxidation states of Cu and Bi by tuning the surface oxygen vacancy (OV) content via a one-pot solution-based in situ H*-mediated reduction method. The resulting BiCuOx catalyst exhibits an enlarged surface area, abundant electrochemically active sites, and optimized OV concentration, delivering a high NH3 faradaic efficiency (FE) of 92.27% ± 3.47% and an NH3 yield rate of 4331.25 ± 208.4 μg h−1 mgcat.−1 at −0.8 V vs. RHE. Theoretical calculations reveal that the as-obtained BiCuOx catalyst more effectively suppresses NO2* intermediate poisoning on its surface compared to the single-component Cu catalyst owing to the favorable orbital hybridization between the intermediates and the catalyst surface, thereby facilitating the subsequent steps in the NRA reaction pathway. Furthermore, a zinc-nitrate battery is designed by integrating a BiCuOx cathode with a zinc plate anode sourced from spent zinc-carbon batteries, achieving a peak power density of 1.706 mW cm−2 and an NH3 FE of 82.31%. This study highlights a low-cost and highly active oxygen vacancy-mediated catalyst for electrochemical NRA through one-pot solution synthesis, promoting green ammonia production via sustainable NRA.
