Transition metal doping has been applied not only to modify the photoactivity of TiO2 but also to influence the product selectivity. For example, mesoporous silica-supported Cu/TiO2 nanocomposites Quizartinib showed significantly enhanced CO2 photoreduction rates due to the synergistic combination of Cu deposition and high surface area SiO2 support [3]. Dispersing Ce-TiO2 nanoparticles on mesoporous SBA-15 support

was reported to further enhance both CO and CH4 production due to the modification of TiO2 with Ce significantly stabilized the TiO2 anatase phase and increased the specific surface area [4]. However, increasing the content of metal dopant does not always lead to better photocatalytic activity. The promotion of the recombination efficiency of the electron-hole pairs may be due to excessively doped transition metal. Besides, nonmetal-doped TiO2 have been used as visible BAY 73-4506 research buy light-responsive photocatalysts for CO2 photoreduction. Significant enhancement of CO2 photoreduction to CO had been reported for I-doped TiO2 due to the extension of TiO2 absorption spectra to the visible light region by I doping [5]. Enhanced visible light-responsive activity for CO2 photoreduction was obtained over mesoporous N-doped TiO2 with noble metal

loading [6]. Nitrogen doping into TiO2 matrix is more beneficial from the viewpoint of its comparable atomic size with oxygen, small ionization energy, metastable center formation and stability. However, a main drawback of N doping is that only relatively low concentrations of N dopants can be implanted in TiO2. In order to overcome the abovementioned limitations, modified TiO2 by means of nonmetal and metal co-doping was investigated as an effective method to improve the photocatalytic activity. Among the current research of single ion doping into anatase TiO2, N-doping and V-doping are noteworthy. Firstly, both elements are close neighbors of the elements they replace in the periodic table. They also share certain similar physical and chemical characteristics with the replaced elements. Secondly, impurity states of N dopants act as shallow acceptor levels, while those

of V dopants act as shallow donor levels. This result in less recombination 4��8C centers in the forbidden band of TiO2 and thus prolongs the lifetime of photoexcited carriers [7]. So the co-doping of V and N into the TiO2 lattice is of particular significance. Recently, V and N co-doped TiO2 nanocatalysts showed enhanced photocatalytic activities for the degradation of methylene blue compared with mono-doped TiO2[8]. Wang et al. synthesized V-N co-doped TiO2 nanocatalysts using a novel two-phase hydrothermal method applied in hazardous PCP-Na decomposition [9]. Theoretical and simulation work also found that N-V co-doping could broaden the absorption spectrum of anatase TiO2 to the visible light region and increase its quantum efficiency [10].