Theoretical insights into heteronuclear dual metals on non-metal doped graphene for nitrogen reduction reaction

Electrochemical nitrogen reduction reaction (eNRR) is a promising strategy for sustainable ammonia production. To achieve high yield and energy efficiency, single-atom dispersion on nitrogen-doped graphene nanosheets has been extensively explored as an electrocatalyst for eNRR. However, challenges remain owing to the high overpotentials arising from unitary active sites and unabundant ligands. In this study, heteronuclear dual-metal catalysts with different non-metals doped in a graphene frame were computationally designed. After a two-step scanning based on density functional theory calculations, five candidates, namely FeMo-S, RuMo-B, RuMo-P, RuMo-S, and RuW-S, were identified as promising catalysts with calculated onset potentials of –0.18, –0.25, –0.27, –0.29, and –0.24 V, respectively. These catalysts can also effectively suppress the competitive hydrogen evolution reaction during NRR. Such excellent catalytic performance origins from two synergetic effects: (1) the cooperation of heteronuclear metals contribute to the electron transfer from active sites to the anti-bonding orbitals of N2 molecules adsorbed on catalysts to effectively activate N≡N bonds; (2) metal-ligands (non-metals) interactions moderate the binding strength of intermediates to slab, which is one of reasons for low NRR onset potential and high NH3 selectivity. The present study provides a theoretical understanding of the NRR mechanism of dual-metal catalysts, offering useful guidance for the rational design of catalysts with high selectivity and activity for NRR.