Electrochemical nitrate reduction to ammonia on CuCo nanowires at practical level

Abstract

Electrochemical reduction of nitrate (NO3RR) holds great promise for environmentally friendly ammonia production. Tandem catalysis is a promising strategy for boosting the NO3RR and inhibiting side effects, but it is still challenged by lacking well-designed catalysts to drive this catalytic process. Herein, the study develops the CuCo branched nanowires (CuCo NW) catalyst, which efficiently converts NO3 − to NH3 on Co (111) and Cu (111) crystal facets through a tandem catalysis mechanism. The in situ grown CuCo NW on Cu foam demonstrates a remarkable Faraday efficiency of 90.3% at 1.0 A cm−2 and maintains stable operation for 200 h at 100 and 200 mA cm−2 in a flow reactor. Density functional theory calculations suggest that the initial absorption and subsequent deoxygenation of *NO3 on Co (111) leading to the formation of *NO2, followed by its transfer to Cu (111) and further conversion to *NH3, establish an optimal pathway by managing rate-determining steps on individual surfaces for NO3RR. To showcase the practical application of the catalyst, the study further develops a scaling-up prototype reactor for continuous ammonia production, realizing the gram-level yield rate of 1474.09 mg h−1 and Faraday efficiency of 91.26% at practical-level 20.0 A.