▎ 摘　　要

The synthesis of ammonia (NH3) through the electrochemical reduction of molecular nitrogen (N-2) is a promising strategy for significantly reducing energy consumption compared to traditional industrial processes. Herein, we report the design of a series of monovacancy and divacancy defective graphenes decorated with single 3d transition metal atoms (TM@MVG and TM@DVG; TM=Sc Zn) as electrocatalysts for the nitrogen-reduction reaction (NRR) aided by density functional theory (DFT) calculations. By comparing energies for N-2 adsorption as well as the free energies associated with *N-2 activation and *N2H formation, we successfully identified V@MVG, with the lowest potential of -0.63 V, to be an effective catalytic substrate for the NRR in an enzymatic mechanism. Electronic properties, including Bader charges, charge density differences, partial densities of states, and crystal orbital Hamilton populations, are further analyzed in detail. We believe that these results help to explain recent observations in this field and provide guidance for the exploration of efficient electrocatalysts for the NRR.