Oxygen Vacancies Mediated Complete Visible Light NO Oxidation via Side-On Bridging Superoxide Radicals

It is of a great challenge to seek for semiconductor photocatalysts with prominent reactivity to remove kinetically inert dilute NO without NO₂ emission. In this study, complete visible light NO oxidation mediated by O₂ is achieved over a defect-engineered BiOCl with selectivity exceeding 99%. Well-designed oxygen vacancies on the prototypical (001) surface of BiOCl favored the possible formation of geometric-favorable superoxide radicals (•O₂^-) in a side-on bridging mode under ambient condition, which thermodynamically suppressed the terminal end-on •O₂^- associated NO₂ emission in case of higher temperatures, and thus selectively oxidized NO to nitrate. These findings can help us to understand the intriguing surface chemistry of photocatalytic NO oxidation and design highly efficient NO _x removal systems.