ELECTRONIC STRUCTURES OF S-DOPED ANATASE AND RUTILE TiO2
Abstract
The electronic structures of S-doped TiO2 have been carried out by first-principles calculations based on density functional theory with plane-wave ultrasoft pseudopotential method. Comparing anion doping with cation doping in anatase and rutile, we found different energy band structures and origins of photoactivity of S-doped TiO2. For anion-doped TiO2, new S–3p bands appear and which lie slightly above the top of the O–2p valence band. It plays a significant role in increasing absorbance in the visible region, resulting in improvement in photocatalytic activity under visible-light irradiation. For cation-doped TiO2, the potential of the O–2p valence band shift much downwards, yielding the stronger oxidative power than that of undoped and S anion-doped TiO2. Nevertheless, the deep impurity states in BG (bond gap) that originate from the S-dopant have negative effects on the recombination of the photoexcited electrons and holes. From our calculated results, we can explain their differences in photocatalytic activity under visible-light irradiation.
