First-principles calculations on electronic structures of N/V-doped and N-V-dodoped anatase TiO2 (101) surfaces.

The energetic and electronic properties of N/V-doped and N-V-codoped anatase TiO(2) (101) surfaces are investigated by first-principles calculations, with the aim to elucidate the relationship between the electronic structure and the photocatalytic performance of N-V-codoped TiO(2). Several substitutional and interstitial configurations for the N and/or V impurities in the bulk phase and on the surface are studied, and the relative stability of different doping configurations is compared by the impurity formation energy. Systematic calculations reveal that N and V impurities can be encapsulated by TiO(2) to form stable structures as a result of strong N-V interactions both in the bulk and the surface model. Through analyzing and comparing the electronic structures of different doping systems, the synergistic doping effects are discussed in detail. Based on these discussions, we suggest that N(O)V(Ti) codoping cannot only narrow the band gap of anatase TiO(2), but also forms impurity states, which are propitious for the separation of photoexcited electron-hole pairs. In the case of N(O)V(Ti) -codoped TiO(2) (101) surfaces, this phenomenon is especially prominent. Finally, a feasible synthesis route for N(O)V(Ti) codoping into anatase TiO(2) is proposed.