Dramatic promotion of visible-light photoreactivity of TiO2 hollow microspheres towards NO oxidation by introduction of oxygen vacancy

Abstract Hollow-structured TiO 2 has attracted much attention owing to its low density, good light-reflecting ability, and excellent permeability. However, the wide bandgap (about 3.2 eV for anatase TiO 2 ) and fast recombination of photo-generated carriers hamper its practical application. Herein, oxygen vacancy (O V ) was introduced onto the surface of TiO 2 hollow microspheres (TiO 2 -HMSs) by a facile method through calcination of the mixture of hydrogen titanate hollow microspheres (H 2 TiO 3 -HMSs) and urea. Using this strategy, both the aims of extending the light-response range and promoting the separation of photo-generated carriers were satisfactorily achieved. The introduction of Ov facilitates the adsorption and activation of NO and O 2 on the surface of TiO 2 -HMSs. This stimulates the production of reactive oxygen species, such as superoxide radicals (•O 2 -) and hydroxyl radicals ( OH), resulting in the dramatic promotion of visible-light photocatalytic oxidation of NO.