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

ABSTRACT

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 (*NOx, 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 (FENH3) of 97.5% and a yield (YNH3) of 470 µmol h-1 cm-2 at -0.6 V, both of which largely surpass the Cu/Cu2O catalyst.