Rational regulation of efficient nitrogen-bridge heteronuclear metal electrocatalyst for nitrogen fixation

Abstract

As an extension of single-atom catalysts (SACs), bimetallic atom catalysts (BACs) have the advantages of higher metal loading, more flexible active sites, and potentially better catalytic performance. However, how to adjust the synergistic effect of two adjacent metal centers to improve the catalytic performance is imperative and challenging. In this work, different transition-metal (TM) atoms (V, Mn, Fe, Co, and Mo) were paired to form 10 kinds of N-bridge heteronuclear bimetals embedded into N-doped graphene, and the electrocatalytic performance of M1M2@NGs for N₂ reduction were predicted by using density functional theory (DFT) computations. By investigating the stability, activity, and selectivity, VMn@NG, VFe@NG, and VCo@NG are screened out as efficient catalysts for activating nitrogen and suppressing the competing hydrogen evolution reaction with low limiting potentials −0.35, −0.29, and −0.31 V for nitrogen reduction reaction (NRR), respectively. The electronic redistribution induced by the adjacent TM-N₄ moieties regulates the interaction between *N₂ intermediates and metal center thus accelerating NRR. The distribution of metal d orbitals can also be used to determine the dominant configuration of N₂ adsorption. Highly efficient and selective BACs for NRR can be screened based on the scaling relationship between the key intermediates (*N₂H and *NH₂). This work not only explores promising electrocatalysts for dinitrogen reduction but also paves a potential route for rationally designing heteronuclear double-site catalysts for other reactions.