Highly efficient visible-light driven photocatalyst with enhanced charge separation prepared by annealing continuously in ammonia and vacuum

• A high efficiently visible light driven photocatalyst was prepared by a simple and economical method.
• The high concentration of gaseous benzene can be fast decomposed by the photocatalyst under visible light illumination.
• The oxygen vacancy introduced by vacuum treatment can trap photogenerated electron efficiently.
• The increased amounts of active centers may be also induced by vacuum treatment.

A highly efficient visible light driven photocatalyst was prepared by annealing samples continuously in ammonia and vacuum. The dependence of photocatalytic activity on calcination temperature was investigated. The effect of annealing temperature on crystal structure, particle size, chemical composition and optical absorbance of TiO2 nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy and UV–visible diffuse reflectance spectroscopy, respectively. The photocatalytic degradation of benzene under visible light illumination demonstrated that the photocatalyst annealed at 600 °C (NV-TiO2-T600) possessed the best photocatalytic property. The excellent photocatalytic activity of NV-TiO2-T600 was attributed to the high crystallinity, strong light-harvesting and enhanced separation of photo-generated electron–hole pairs. The vacuum treatment had a positive effect on enhancing charge separation. In addition, the increased amount of surface oxygen vacancy might be the crucial factor for the improvement of photocatalytic activity.

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