Electronic structure analysis of light-element-doped anatase TiO2 using all-electron GW approach

A new structural phase of anatase TiO2 codoped with C and N with a relatively low band gap was discovered. Phase stability was first analyzed using density functional theory calculations by considering interstitial and substitutional positions and oxygen vacancies. The stable defect states were found to depend on the oxygen (O2) pressure conditions or oxygen chemical potential in C and N monodoped and codoped TiO2. Thereafter, the all-electron GW approach based on many-body perturbation theory was adopted to determine the electronic structures and understand the band gap narrowing mechanism. The band gap could be controlled by varying the oxygen pressure and doping states, and the band gap narrowing due to C, N codoping was more than that due to monodoping. Under an intermediate oxygen pressure condition, the band gap of TiO2 codoped with C and N was found to be 2.28 eV. Therefore, TiO2 codoped with C and N can be used as a visible-light-response photocatalyst.