NiO-Incorporated Cu/Cu₂O Nanowires for Highly Efficient Electrochemical Nitrate Reduction to Ammonia

Electrochemical nitrate reduction to ammonia (NRA) is a promising sustainable way to synthesize ammonia (NH₃) from nitrate (NO₃ ^-) contaminants. Cu-based electrocatalysts are frequently utilized for NRA due to their strong NO₃ ^- adsorption and de-oxygenation ability. However, this kind of catalyst usually possesses the weak water dissociation ability, resulting in insufficient proton supply in alkaline media to retard the following hydrogenation step of O-containing intermediates (*NO_x, typically NO₂ ^-) to target NH₃. Herein, NiO-incorporated Cu/Cu₂O nanowires grown on nickel foam (p-CuNi@NF, p refers to plasma treatment) were synthesized via hydrothermal growth and subsequent O₂ plasma treatment for efficient NRA electrocatalysis. On this p-CuNi@NF catalyst, NiO is able to accelerate the hydrogenation step by promoting the water dissociation to provide protons, ultimately facilitating efficient NRA. p-CuNi@NF exhibits excellent NH₃ selectivity and yield in a wide potential range and reaches a high Faradaic efficiency (FE_NH3) of 97.5 % and a yield (Y_NH3) of 470 μmol h^-1 cm^-2 at -0.6 V, both of which largely surpass the Cu/Cu₂O catalyst.