Computational Investigation of Transition Metal Atom-Decorated C₈N₈ Monolayers for Nitrogen Reduction Reaction

The electrocatalytic nitrogen reduction reaction (NRR) is regarded as a promising approach for sustainable ammonia synthesis. Developing highly active and selective catalysts remains a key challenge for this technology. C₈N₈ serves as an excellent support for anchoring the single atoms due to its unique structures and high porosity. In this work, the catalytic performance of transition metal single-atom-decorated C₈N₈ monolayers toward the NRR using density functional theory calculations is comprehensively studied. Among varied combinations, 24 candidates are screened out that are expected to be stable as indicated by negative binding energy (E_b < 0) and negative formation energy (E_f < 0). Among these, TiC₈N₈, MoC₈N₈, and OsC₈N₈ exhibit relatively low reaction barriers of 0.67, 0.50, and 0.21 eV, suggesting potential catalytic activities. Especially, OsC₈N₈ shows relatively good selectivity for the NRR compared with TiC₈N₈ and MoC₈N₈. Electronic structure analysis reveals that OsC₈N₈ effectively weakens the NN bond, facilitating N₂ activation. This work provides valuable insights into the material design for nitrogen reduction electrocatalysis and offers feasible candidates for the experimental synthesis.