摘要: The reduction of N2 to NH3 is an important reaction for the industrial production of ammonia gas. Here, we theoretically studied the thermal synthesis of ammonia catalyzed by Ru1@Mo2COx single-atom catalyst, where Ru atoms are anchored on the oxygen vacancy of the defective Mo2COx. The results show that Ru1@Mo2COx exhibits excellent stability. Moreover, Ru1@Mo2COx can effectively adsorb and activate N2, owing to up to −0.87 |e| charge transfer from Ru1@Mo2COx to N2. The optimal pathway of N2-to-NH3 conversion is association pathway I, of which the rate-determining step is *NH2→*NH3 with of barrier energy of 1.26 eV. Especially, the Mo2COx center functions as an electron reservoir, donating electrons to the NxHy species, while the Ru single atom serves as a charge transfer pathway, thereby enhancing the reaction activity. This finding provides a theoretical foundation for the rational design of MXene-based single-atom catalysts for thermal catalytic NH3 synthesis.