Abstract:

Electronic structures of nitrogen(N)/fluorine (F)-doped and N-F-codoped TiO2 anatase (101) surfaces were investigated by density functional theory (DFT) plane-wave pseudopotential method. Since DFT calculations performed on transition metal oxides always lead to a severe underestimation of the band gap, DFT+U (Hubbard coefficient) method was also adopted to calculate the electronic structures. DFT results demonstrated that mixing of N 2p states with O 2p and Ti 3d valence band (VB) states contributes to the band gap reduction of TiO2 whereas F doping and the introduction of oxygen vacancies have no obvious effect on the electronic structure. However, from DFT+U, no obvious band gap narrowing was observed by N-doping except for the isolated N 2p states lying in the gap. In DFT+U calculation, F-doping as well as the introduction of oxygen vacancies leads to an obvious band gap narrowing. Results from DFT+U calculations accord well with some experimental results.

Key words: TiO2 anatase (101) surface, Nitrogen/fluorin-doped, First-principles calculation, Electronic