Boosting electrochemical urea synthesis via nitrous oxide and carbon oxide coupling over homonuclear dual-atom catalysts: a computational study

Abstract

Developing efficient electrocatalysts for urea synthesis is attracting increasing attention but remains challenging due to the lack of simplified mechanisms and suitable feedstock. In this work, urea synthesis on dual transition metal atom-anchored graphitic carbon nitride (TM₂@g-C₂N) via N₂O and CO as N and C sources was investigated using density functional theory (DFT) calculations. By employing a three-step screening strategy, we systematically studied homonuclear dual-atom pairs embedded in g-C₂N for their catalytic stability, activity, and selectivity. The results demonstrate that dual-atom pairs can be stably embedded into the hollow regions of g-C₂N via nitrogen coordination and exhibit superior electrochemical stability. In addition, dual-metal atoms significantly enhance the electrical conductivity of g-C₂N, facilitating charge transfer. Notably, Fe₂ and Co₂@g-C₂N emerge as promising candidates for electrocatalytic urea synthesis via CO and N₂O coupling, with limiting potentials (U_L) of −0.27 V and −0.35 V, respectively, following an alternative mechanism. Meanwhile, Nb₂@g-C₂N is identified as an excellent catalyst for N₂O reduction to NH₃, achieving a U_L of −0.34 V with a mixed mechanism. We further reveal that stable *NCON adsorption promotes subsequent hydrogenation steps, lowering the limiting potential for urea formation on Fe₂@g-C₂N. The adsorption of N₂O and formation of *NCON on TM₂@g-C₂N are identified as critical steps, where the relatively strong interactions between active sites and intermediates correlate with high catalytic activity. This work expands the potential of dual-atom catalysts in enabling efficient urea production via N₂O and CO resources.