LAUSR

Surface vacancy engineering holds great promise for boosting the electrocatalytic activity for CO2 reduction reaction; however, the vacancies are generally unstable and may degrade into the inactive phase during electrolysis. Stabilizing the vacancy-enriched structure by heteroatoms can be an effective strategy to get a robust and active catalyst. Herein, a nitrogen-vacancy enriched Nb4 N5 on N-doped carbons is constructed, which is thereafter stabilized by a self-enhanced oxygen doping process. This oxygen-doped complex is used as an effective CO2 catalyst, which exhibits a maximum CO Faradaic efficiency of 91% at -0.8 V (vs reversible hydrogen electrode, RHE) and long-term stability throughout 30 h of electrocatalysis. Density function theory calculations suggest that the incorporation of oxygen in Nb4 N5 facilitates the formation of *COOH and thus promotes the CO2 reduction.