Synthesis of visible-light-active TiO2-based photocatalysts by carbon and nitrogen doping

TiO₂ has been considered the most promising photocatalyst for the degradation of pollutants in air or water; however, it shows poor absorption of visible light and requires ultraviolet (UV) light for activation. We have successfully synthesized a visible-light-active carbon and nitrogen co-doped TiO₂ catalyst. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and N₂ desorption-adsorption. Our results demonstrate that the optical response of TiO₂ was shifted from UV to the visible light region with the introduction of carbon and nitrogen. Nitrogen was substituted for some of the lattice oxygen atoms, and most of the carbon was in the form of elemental carbon. The surface area of the co-doped catalyst was increased, and its photocatalytic efficiency was enhanced. The photocatalytic tests indicated that the co-doped catalyst demonstrated higher activity for the degradation of methylene blue (MB) compared with pure TiO₂ both under visible light and UV irradiation, attributed to the synergetic effects of carbon and nitrogen dopants.