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 (O22-) species, without superoxide (O2-) formation, on O2-exposed V2O5-x surfaces containing a high density of oxygen vacancy (VO) defects. Here, we unveil the mechanism of surface-adsorbed O22- formation and show its correlation with the unusual electronic band structure of V2O5. Results show that O22- formation does not occur through the traditional Mars-van Krevelen (MvK) mechanism. Rather, the high density of degenerate conduction band electrons on the V2O5-x surfaces induces spontaneous O22- 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.