Photocatalytic Removal of NOx over Visible Light Responsive Oxygen-Deficient TiO₂

Oxygen-deficient TiO 2 was prepared with a low-temperature method and utilized in photocatalytic removal of gaseous NO at the 400 ppbv level in air under visible light (420 nm < λ < 700 nm) irradiation. Catalysts synthesized at 200 °C (TiO 2 -200) exhibited the highest ability to remove the NO gas in air under visible light irradiation. A higher oxidation ability for NO 2 to NO 3 – leads to a higher conversion of NO x on TiO 2 -200. The relationship between the physicochemical properties and the photocatalytic performance of the as-prepared catalyst is discussed. The large surface area of TiO 2 -200 can provide more active sites for the reaction. The oxygen vacancies of TiO 2 -200 can effectively expand the absorption of visible light and accelerate the separation of photogenerated electrons and holes. The first-principles density functional theory (DFT) calculation further confirms the role of oxygen vacancies on the narrowing of the band gap and separating of photogenerated electron–hole pairs.