▎ 摘　　要

Developing stable and efficient catalysts for the electroreduction of nitrogen remains a huge challenge and single atom catalysts (SACs) are expected to achieve relatively high ammonia selectivity at low applied potential. Based on density functional theory calculations, the potential application of 27 single transition metal (TM = Sc-Zn, Y-Ag, Hf-Au) atoms supported by N(O)-dualdoped graphene (TM-O2N2/G) for the electroreduction of nitrogen is intensively investigated. At low nitrogen coverage, W(Mo, Nb, Ta)-O2N2/G are predicted to yield low ammonia selectivity (< 13%) at limiting-potential of -0.58, -0.53, -0.56, and -0.76 V starting from adsorbed nitrogen with side-on mode, respectively. With the increasing N-2 coverage, the TM-O2N2/G is reconstructed as TM-(N-2)(2)N-2/graphene. The electroreduction of nitrogen proceeds from end-on adsorbed nitrogen molecule with high ammonia selectivity, and the limiting-potentials are theoretically predicted as -0.20, -0.40, -0.29, and -0.21 V on W(Mo, Nb, Ta)-(N2)2N(2)/G, respectively. It is suggested that utilizing the reorganization of local coordination environments of SACs by high coverage of reactant molecules under reaction condition can not only enhance the activity at lower limiting-potential but also improve the ammonia selectivity.