Boosting electrochemical urea synthesis via nitrous oxide and carbon oxide coupling over homonuclear dual-atom catalysts：a density functional study: 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, we propose a novel mechanism for urea synthesis on dual transition metal atom-anchored graphitic carbon nitride (TM2@g-C₂N) through the co-reduction of CO and N2O using density functional theory (DFT) calculations. By employing a three-step screening strategy, we systematically investigated homonuclear dual-atom pairs embedded in g-C₂N for their catalytic activity, selectivity, and stability. Our results demonstrate that dual-atom pairs can be stably embedded into the hollow regions of g-C2N via nitrogen coordination, exhibiting 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 (UL) of −0.27 V and −0.35 V, respectively, following alternative mechanism. Meanwhile, Nb2@g-C2N is identified as an excellent catalyst for N2O reduction to NH3, achieving UL of −0.34 V within 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 co-reduction.