Impact of sulfur-, tantalum-, or co-doping on the electronic structure of anatase titanium dioxide: A systematic density functional theory investigation

In order to achieve the purpose of further improving the photocatalytic performance of sulfur (S)-doped anatatse titanium dioxide (TiO2) and providing an example to design an efficient photocatalyst, the electronic and optical properties of pure, S-doped, tantalum (Ta)-doped and S+Ta-codoped anatase TiO2 were systematically investigated by using the density functional theory within a GGA+U method. The results indicate that Ta codoping could improve the S incorporated into TiO2 lattice under reducing conditions. And the incorporation of Ta into S-doped TiO2 further increases the photocatalytic activity under visible-light irradiation compared with that of the S-doped TiO2: the distance from S-related impurity energy levels to the top of valence band is obviously decreased in S+Ta-codoped TiO2; and the calculated band gap of S+Ta-codoped TiO2 is smaller than that of S-doped TiO2; furthermore, through the synergistic effects between S and Ta, S+Ta-codoped TiO2 not only has the similar high absorption rate to S-doped TiO2 in the UV-light region, but also has higher absorption rate than S/Ta-doped TiO2 in the visible-light region.