Enhanced nitrogen electroreduction performance by the reorganization of local coordination environment of supported single atom on N(O)-dual-doped graphene

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)-dual-doped 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 N₂ coverage, the TM-O₂N₂/G is reconstructed as TM-(N₂)₂N₂/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)₂N₂/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.