Synergetic effect between non-metals and dual metal catalysts for nitrogen reduction reaction

Abstract

Nitrogen reduction reaction (NRR) is an essential process for ammonia synthesis. Currently, such process is overwhelmingly catalyzed with iron-based metal catalysts and still confronts the big challenge of high overpotential when room-temperature electrosynthesis is targeted due to the intrinsic inertness of NN bond in N₂. In this study, dual metal catalysts have been computationally designed and modulated by different non-metals dispersed in a graphene frame. As scanned by density functional theory (DFT) calculations, five candidates, namely Fe₂@SN₄, Fe₂@BN₄, Co₂@BN₄, Co₂@PN₄ and Ni₂@PN₄ catalysts, have been identified as promising catalysts with a calculated onset potential of −0.20, −0.27, −0.36, −0.34, and −0.33 V, respectively; more importantly, the competitive hydrogen evolution reaction (HER) can be well suppressed during the NRR. Such excellent catalytic performance origins from two synergetic effects, including the metal–metal and metal–ligands (non-metals) interactions, both of which can promote the electron transfer from d-orbitals of metal atom pair to the anti-bonding orbitals of adsorbed N₂ molecules. This can effectively activate the NN bond, resulting in low NRR onset potential and high NH₃ selectivity. The presented theoretical effort advances the theoretical understanding and provides guidance for the rational design of advanced non-precious NRR catalysts with high efficiency and selectivity.