Operando Formed Co–Cu Metal/Oxide Nanosheets for Efficient Nitrate Reduction to Ammonia

Electrocatalytic reduction of nitrate to ammonia (NRA) is an effective way to achieve environmental remediation and convert waste into treasure. However, this reaction requires multielectron and proton transfer, and the hydrogen evolution reaction (HER) is the competitive reaction during NRA. Therefore, it is urgent to design a reasonable catalyst to improve the activity and selectivity of NRA. In this study, CoCu oxide nanosheets were prepared on Cu foam (CoCu/CF) as an electrocatalyst for NRA via a one-step hydrothermal method, which is simple and rapid with mild conditions. The catalyst can effectively remove NO3– through the synergistic effect of combining two active components (Co/CoOx and Cu/CuOx). The Cu2O/Cu promoted the reduction of NO3– to NO2–, and CoO/Co enhanced the adsorption/dissociation of H2O to provide adsorption H (H*) for the hydrogenation step. Therefore, CoCu/CF exhibited outstanding electrocatalytic performance for NRA, including an ammonia yield (YNH3) of 561.29 μmol h–1 cm–2 and a Faraday efficiency of 91.84% for ammonia (FENH3).