Bimetallic supported on graphene as an efficient electrocatalyst for nitrogen fixation: the search of the optimal coordination atoms

: Electrocatalytic nitrogen reduction reaction (NRR) is the most attractive way for ammonia synthesis, thus the development of catalyst with excellent activity, high NRR selectivity, and long-term durability is crucial but remains a great challenge. Herein, by means of density functional theory calculations, we systematically investigated the stability and catalytic performance of the anchored bimetals, pairing of different transition metal atoms (Mo, Cr, Ti, V, Ru, and W), on graphene with different coordination atoms (C, N, O, P, and S) for N 2  fixation. By screening the stability, limiting potential, and selectivity of 105 candidates, we found that the carbon is the optimal coordination atom for bimetallic pairs, whereas the other four coordination atoms are unsatisfactory due to the thermodynamic unstable anchor sites for bimetallic pairs (O, P, and S atoms) and relatively low catalytic activity (N atom). Notably, the bimetal of Mo and Ti supported on C-coordinated graphene (MoTi-CG) and TiV-CG are predicted as effective NRR catalysts with the attractive limiting potential of -0.34 and -0.30 V. Furthermore, the volcano curve between the limiting potential and the adsorption free energy of NH 2 * (ΔG(NH 2 *)) is revealed, in which a moderate ΔG(NH 2 *) is required for high activity NRR catalysts. This study not only provides a theoretical basis for the rational design of bimetal anchored graphene as effective NRR catalysts under ambient conditions, but also opens up a new idea to accelerate the screening of NRR catalysts.