Search

The supercells of pure anatase TiO2, nitrogen and/or vanadium doping anatase TiO2 were calculated by first-principles with the plane-wave ultrasoft pesudopotentials method. The effects of different ions doping on the crystal structure, electronic structure, optical properties and photocatalytic activity were investigated by means of the calculational data. At the same time realizing visible-light response, nitrogen and vanadium codoping TiO2 photocatalysts have strong redox potential, and its photocatalytic efficiency would be remarkably improved due to enhancement of electron–hole pairs’ separation. The conclusions would have important significance for understanding and further developing of TiO2 photocatalyst that are activity under visible-light irradiation. [ABSTRACT FROM AUTHOR]

The vanadium-doped TiO2 nanoparticles were prepared by a sol-gel method with Ti(OBu)4 as a precursor. The powders were characterized by XRD, FT-IR, TEM, XPS and UV-Vis absorption spectrum. The photocatalytic activity of the powders for methyl orange degradation was investigated under a fluorescent lamp. The results show that the doping V presents mainly in the form of V5+, and vanadium doping can restrain the crystal growth and promote the phase transfer from anatase to rutile. Vanadium doping can widen the light absorption range of TiO2, and the absorption threshold wavelength is red shifted from 380 nm to about 650 nm. As a result, the photocatalytic activity of the V-TiO2 nanoparticles is higher than that of P25 under the fluorescent lamp. [ABSTRACT FROM AUTHOR]

We have systematically investigated the modification mechanism of anatase TiO2 doped with nitrogen using the plane-wave ultrasoft pseudopotentials method based on density functional theory. The crystal structure, impurity formation energy, electronic structure and optical properties of TiO2 supercells containing subsitutional nitrogen, interstitial nitrogen or oxygen vacancies were calculated. TiO2 doped with substitutional nitrogen has shallow acceptor states above the valence band. In contrast, TiO2 doped with interstitial nitrogen has isolated impurity states in the middle of the band gap. These impurity energy levels are mainly hybridized by N 2p states with O 2p states and Ti 3d states. TiO2 containing oxygen vacancy has shallow donor states below the conduction band, which consists of Ti 3d states. Except for containing oxygen vacancies, the band gaps of N-doped TiO2 are narrowed in the range 0.03-0.23 eV, and thus their fundamental absorption edges extend to the visible-light region. By nitrogen doping, the octahedral dipole moments in TiO2 increase due to the changes in lattice parameters, bond length and charges on atoms, which is very effective for the separation of photoexcited electron-hole pairs. The calculated results are consistent with the existing experimental data. Based on these results, the effects on the electronic structure and photocatalytic activity of anatase TiO2 doped with nitrogen were analysed and compared in detail, and the mechanism by which anatase TiO2 doped with nitrogen has higher photocatalytic activity than that of pure TiO2 was explained. The conclusions have important significance for understanding and further developing TiO2 photocatalysts that are active under visible-light irradiation. [ABSTRACT FROM AUTHOR]