Enhanced electrochemical nitrate reduction on copper nitride with moderate intermediates adsorption

Nitrate in surface and underground water caused systematic risk to the ecological environment. The electrochemically reduction of nitrate into ammonia (NO3RR), offering a sustainable route for nitrate containing wastewater treatment and ammonia fertilizer conversion. Exploration of improved catalysts activity with lower energy barriers is still challenging. Herein, we present a copper nitride (Cu3N) catalyst with moderate *NOx and·H2O intermediates adsorptions showed enhanced NO3RR performance. Density functional theory calculations reveals that the unique electronic structure of Cu3N provides efficient active sites for NO3RR, and enables balanced adsorption of *NO3 and·H2O (ΔE descriptor) and moderate intermediate (*NO3 → HNO3, *NH2→*NH3) adsorption energy. Interestingly, in-situ analysis proved the potential-driven reconstruction and rehabilitation of Cu3N, thus implied for better mechanism understanding. The NO3RR activity of Cu3N surpasses that of most recent catalysts and demonstrates superior stability and implies the application for NH4+ fertilizer recovery, which maintaining an NH3 Faradaic efficiency of 93.1 % and high yield rate of 2.9 mg cm2h−1 at −0.6 V versus RHE.