Modulating Metal-Nitrogen Coupling in Anti-Perovskite Nitride via Cation Doping for Efficient Reduction of Nitrate to Ammonia.

Abstract

The complexes of metal center and nitrogen ligands are the most representative systems for catalyzing hydrogenation reactions in small molecule conversion. Developing heterogenous catalysts with similar active metal-nitrogen functional centers, nevertheless, still remains challenging. In this work, we demonstrate that the metal-nitrogen coupling in anti-perovskite Co4N can be effective modulated by Cu doping to form Co3CuN, leading to strongly promoted hydrogenation process during electrochemical reduction of nitrate (NO3-RR) to ammonia. The combination of advanced spectroscopic techniques and density functional theory calculations reveal that Cu dopants strengthen the Co-N bond and upshifted the metal d-band towards the Fermi level, promoting the adsorption of NO3- and *H and facilitating the transition from *NO2/*NO to *NO2H/*NOH. Consequently, the Co3CuN delivers noticeably better NO3-RR activity than the pristine Co4N, with optimal Faradaic efficiency of 97% and ammonia yield of 455.3 mmol h-1 cm-2 at -0.3 V vs. RHE. This work provides an effective strategy for developing high-performance heterogenous catalyst for electrochemical synthesis.