Regulating the coordination environment of single-atom catalysts anchored on nitrogen-doped graphene for efficient nitrogen reduction†

Abstract

Electrocatalysts with excellent selectivity and activity towards the target product are pivotal for N2 conversion and utilization. In this study, we systematically explored the nitrogen reduction reaction (NRR) catalytic performance of Mo-based single-atom catalysts (Mo-N₄-SACs) through density functional theory (DFT) calculations. We changed the coordination environment of the single atom by placing the active center of the SACs at the edge or basal plane of N-doped graphene or changing the coordination atom of the active center. Among the four Mo-N₄-SACs studied, Mo-ZZG demonstrated remarkable catalytic activity and selectivity for N₂ reduction to NH₃ with a limiting potential (U_L) of −0.26 V. After considering the solvation effect, the potential determination step was N₂ → N₂H, and only the U_L was increased, specifically to −0.42 V. In order to reduce the U_L of the Mo-ZZ-edge (−0.85 V) for the NRR by replacing the N atom with an S or O atom, the U_L of the O1-ZZ-edge was reduced to −0.58 V. This well illustrated that the catalytic activity could be effectively improved by rationally adjusting the position and coordination atoms of a single atom. This work provides valuable insights into the rational design and screening of efficient catalysts for N₂ reduction.