Influence of annealing atmosphere for controlling oxygen vacancies of PVP-capped TiO2 nanoparticles

Herein, we report the white light photocatalytic activity of PVP-capped TiO2 nanostructures synthesized through PVP-assisted chemical precipitation technique. The PVP-capped hydrous amorphous titania (PVP-HAT) on thermal treatment at 300 °C introduced excess oxygen vacancies and thereby extended its optical absorption to visible region. Further, the annealing atmosphere such as air, nitrogen, and oxygen determines the nature of dehydration in PVP-HAT and oxygen vacancies. The nitrogen annealed sample exhibited highest optical absorption in the visible region ascribed to rapid dehydration of PVP-HAT resulting in the formation of higher density of non-reactive oxygen vacancies. Besides, the intensity of EPR signal at g = 2.005 ascribed to oxygen vacancies is highest for nitrogen annealed sample. Slow dehydration of PVP-HAT at 300 °C in an oxygen atmosphere gives rise to higher density of active oxygen vacancy sites in PVP-TiO2 nanostructures, which can serve as an active site during photocatalytic degradation of RhB dye upon irradiation with white light.