Theoretical studies of photocatalytic behaviors of isoelectronic Sn/Pb-doped TiO2: DFT+U

First-principles DFT+U method was used to study the electronic structures and photocatalytic behaviors of Sn/Pb atoms doped at the (1 0 1) facet and in the internal bulk of TiO2 anatase phase. Our theoretical calculations revealed that Sn atoms tend to replace the positions of titanium atoms in the interior of the bulk while Pb atom is more likely to substitute it on the surface. The difference between the formation energy of doped atoms occupying the positions of titanium atoms on the surface and in interior is so small that tin/lead atoms can be easily distributed at the (1 0 1) surface and in the internal bulk of titanium dioxide. Those tin ions on the surface and lead ions in the internal bulk can form a localized unoccupied defect level below the bottom of the conduction band. These localized defect state can form electron traps, which delay the recombination time of photogenerated electron-hole pairs and play a key role in photocatalytic performance.