▎ 摘　　要

The electrocatalytic nitrogen reduction reaction (NRR) is a promising strategy to generate NH3 in mild condition. Herein, we designed four NRR single-atom catalysts to mimic the structures of FeMo-cofactor in nitrogenase, in which a Mo or Fe atom is anchored to sulfur doped graphene carbon nanosheets (Mo/Fe@S-gCNS). Density functional theory calculations were performed to investigate the stability of Mo/Fe@S-gCNS, as well as their NRR activity. The results suggest that Mo@S-gCNS coordinated with three S (Mo-S3) displays the best NRR catalytic activity among the four catalysts, and the NRR prefers to proceed through the enzymatic pathway with an overpotential as low as 0.24 V. The outstanding performance is mainly attribute to the appropriate coordination environment together with the intrinsic electronic structure of the embedded Mo atom. These findings contribute to designing the NRR single-atom catalysts and understanding the potential active sites of the FeMocofactor.