(586f) Improved Photocatalytic Activity Under Visible Light Irradiation of Nanosized-TiO2 Co-Doped with Vanadium and Nitrogen

Heterogeneous nanocrystalline titania (TiO₂) has been extensively investigated due to its notable photocatalytic capability for the industrial waste water treatment. However, an obvious problem hindering the application of TiO₂ is its poor response to visible light due to its wide bandgap. Herein, TiO₂ photo-catalyst is synthesized by co-doping vanadium and nitrogen by sol-gel method to sensitize TiO₂ in visible light. The concentrations of V and N were varied and optimized to enhance photo-catalytic activity. In order to increase the active surface area, the crystalline powder was ball milled to nanosize. The photo-catalysts were characterized by XRD, FT-IR, SEM, EDS, BET surface area, XPS, and UV–vis diffuse reflectance spectra. The co-doped TiO₂ nanocrystal has a narrower band gap than singly V-doped TiO₂ and singly N-doped TiO₂. The XPS detected vanadium (V⁴⁺ and V⁵⁺) and nitrogen ions on the surface of photo-catalysts, but no diffractive peak of vanadium oxide or titanium nitride was observed in XRD spectra. High energy ball-milling was able to increase the surface area due to reduction in particle size below 50 nm as confirmed by SEM. The co-doped TiO₂ photo-catalyst showed significantly better photocatalytic activity for the degradation of organic dyes such as Rhodamine B and methylene blue under visible light irradiation (λ > 420 nm) as compared with V-doped TiO₂ and N-doped TiO₂. The incorporation of N and V in TiO₂ lattice induces the appearance of passivated shallow acceptor and donor levels near the valence and conduction band, respectively, causing narrowing of the band gap. In addition, these levels can also act as traps for photoexcited holes or electrons to reduce the recombination between photo-generated charges thus contributing to enhance the photocatalytic activity.