Unraveling the role and mechanism of different vacancies in enhancing NO photocatalytic oxidation on g-C3N4 thin films

Improving the efficiency of nitric oxide (NO) removal while reducing the formation of toxic nitrogen dioxide (NO 2 ) is a challenge. Nonetheless, it remains uncertain regarding the distinct roles of carbon versus nitrogen vacancies in graphitic carbon nitride (g-C 3 N 4 ) in governing the oxidation pathway. In this study, g-C 3 N 4 enriched with carbon or nitrogen vacancies, along with the corresponding polyvinylidene fluoride (PVDF)-supported composite films, are prepared. The adsorptions and anchoring of NO and its intermediates are significantly enhanced by the carbon vacancies. Despite a high free energy barrier of the conversion from nitrite to nitrate, the strong anchoring suppresses the release of gaseous NO 2 . The formation of Nitrogen vacancies gives rise to polarization of the spin, leading to a significant negative displacement of the potential of the conduction band and increased carrier lifetime along with a considerable decrease in the barrier for the conversion of nitrite to nitrate. This mechanism leads to enhanced reaction flux that will improve deep oxidation. The incorporation of these materials into the PVDF film greatly enhances performance and provides reusability. This work elucidates the distinct mechanisms by which carbon and nitrogen vacancies regulate NO oxidation, providing a theoretical basis for designing efficient and selective air purification materials.