Surface-Active Peroxide Formation on V2O5–x and Its Correlation with the Unusual Electronic Band Structure of the Oxide

V₂O₅ is an important catalyst for a wide range of industrial oxidative transformations, including the controlled dehydrogenation of alkanes and other hydrocarbons. In these catalytic transformations, the key step is the addition of molecular O₂ as a cofeed for the regeneration of the catalyst surface. Beyond that, the role of added oxygen, especially in the formation of reactive oxygen species (ROS) that might affect the catalytic selectivity, has been largely unexplored. A recent study reported the observation of peroxide (O₂^2–) species, without superoxide (O₂^–) formation, on O₂-exposed V₂O_5–x surfaces containing a high density of oxygen vacancy (V_O) defects. Here, we unveil the mechanism of surface-adsorbed O₂^2– formation and show its correlation with the unusual electronic band structure of V₂O₅. Results show that O₂^2– formation does not occur through the traditional Mars-van Krevelen (MvK) mechanism. Rather, the high density of degenerate conduction band electrons on the V₂O_5–x surfaces induces spontaneous O₂^2– formation through the process of surface transfer doping to O₂ in the presence of adsorbed water film and H⁺, thus forming a double layer that electrostatically stabilizes the active oxygen species and promotes catalytic transformation.