The structural and electronic properties of Nb doped Rutile TiO2 are investigated by first-principles calculations based on density functional theory. Several doping models including 2(NbTi)+Oi, NbTi+Oi, 2(NbTi), and NbTi are investigated. We find that all the doped systems preserve the semiconductor character but have an impurity state inside the band gap. Therefore, the band gaps of the doped systems are reduced by 0.15 1 . 41 eV, compared to that of the pure rutile TiO2. These results suggest that Nb-doped TiO2 would have higher photocatalytic activity than pure TiO2. The origin of the gap state is different in different doping models. The calculation results show that interstitial oxygen atom play an essential role in manipulating the valence state of Nb impurity. The charge density analysis show that Nb atom in 2(NbTi)+Oi and NbTi+Oi systems can be pentavalent since the Nb atom loses much more electrons due to the interaction with the interstitial oxygen atoms. On the other hand Nb atoms in the NbTi and 2(NbTi) doped systems would be tetravalent.
APS March Meeting Abstracts
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