Regulating intermediate adsorption and HO dissociation on a diatomic catalyst to promote electrocatalytic nitrate reduction to ammonia

Electrochemical conversion of nitrate (NO 3 − ) is an efficient approach to reduce NO 3 − pollutants and it offers a promising alternative for sustainable NH 3 synthesis. However, this process is limited by the mismatched reaction kinetics of NO 3 − discharge, active hydrogen (H*) formation via water dissociation, and stepwise hydrogenation processes. Herein, using density functional theory (DFT) calculations, we screened a library of Cu-M diatomic catalysts coordinated with a N doped carbon matrix (Cu-M-N-C, M = Fe, Co, Ni, Mn, Zn) by balancing N-containing intermediate adsorption and H 2 O dissociation barriers. Among these catalysts, Cu-Fe-N-C demonstrates the best performance with a NH 3 yield rate of 1.22 mmol h −1 cm −2 and a high Faradaic efficiency (FE) for NH 3 synthesis of 95.08% at −0.8 V vs. the reversible hydrogen electrode, in which diatomic sites facilitate the first NO 3 − discharge step to generate adsorbed *NO 3 and lower the energy barriers of the following hydrogenation/dehydration steps. More importantly, the incorporated Fe sites could promote the H 2 O dissociation, providing a large supply of H* for the deep hydrogenation of N-containing intermediates. This work reveals the tunable bonding interactions of diatomic sites with multiple reactant/intermediates, offering a new avenue for rational design of highly efficient atomic-level dispersed catalysts for both NO 3 − abatement and NH 3 synthesis. Cu-Fe-N-C demonstrates excellent electrocatalytic activity for nitrate reduction by optimizing intermediate adsorption and generating a substantial supply of H* for the thorough hydrogenation of the N-containing intermediates.