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

Oxygen-deficient TiO2 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 < lambda < 700 nm) irradiation. Catalysts synthesized at 200 degrees C (TiO2-200) exhibited the highest ability to remove the NO gas in air under visible light irradiation. A higher oxidation ability for NO2 to NO3- leads to a higher conversion of NOx on TiO2-200. The relationship between the physicochemical properties and the photocatalytic performance of the as-prepared catalyst is discussed. The large surface area of TiO2-200 can provide more active sites for the reaction. The oxygen vacancies of TiO2-200 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.