Improved visible light photocatalytic activity of TiO2 co-doped with Vanadium and Nitrogen

V- and N-codoped TiO2 photo-catalyst is synthesized by sol-gel method to sensitize TiO2 to 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 obtain nanosized particles. The photo-catalysts were characterized by Micro-Raman, TEM, XPS and UV-vis (in diffused reflectance mode) techniques. The co-doped TiO2 photocatalyst displayed narrower band gap (2.3 eV) compared to singly doped TiO2 catalyst, namely V (2 at.%)-doped (2.42 eV), N (4 at.%)-doped (2.95 eV), and undoped TiO2 (3.13 eV). The photocatalytic activity for the degradation of Rhodamine B (an organic dye) under visible light irradiation obtained with co-doped TiO2 photo-catalyst is significantly better as compared to the undoped,V-doped, and N-doped TiO2. The incorporation of V and N in TiO2 lattice induces isolated energy levels near the conduction and valence bands, respectively, causing an effective narrowing of the band gap. In addition, due to the low dopants concentrations, these energy levels can also act as traps for photoexcited holes or electrons thus reducing the recombination between photo-generated charges. Both these effects, namely band narrowing and enhanced charge separation produce synergistic effects to increase the photocatalytic activity of V-N-codoped TiO2. (c) 2012 Elsevier B.V. All rights reserved.