Abstract:

The photocatalytic potential of rare earth doped TiO₂(RE/TiO₂) was studied by theoretical and experimental methods. With density functional theory(DFT), the geometries, band structures, density of states and electronic structures of RE/TiO₂ with 16 TiO₂ units in one supercell were calculated at plane wave ultra-soft pseudo-potential level with the exchange and correlation energy of the electrons described as generalized gradient approximation(GGA) of Perdew, Burke and Enzerhof(PBE). The results show that Y, La, Gd, Lu, Ce, Eu, Yb and Tb can promote the photocatalytic activity of TiO₂, while too much of Pr, Nd, Pm, Sm, Dy, Ho, Er and Tm may decrease its photocatalytic activity by forming more orbitals between valence band top and conduction band bottom, which will act as combining centers for electronics and holes. On the other hand, the nine powders of Y, Ce, Pr, Sm, Gd, Dy, Ho, Er or Yb doped TiO₂ were prepared by sol-gel method, and their crystal structures and optical absorption properties were characterized by X-ray diffraction(XRD) and UV-Vis spectrum, respectively. It shows that RE/TiO₂ maintains the same crystal form as anatase TiO₂, and the doping of Ho, Pr, Ce, Sm, Y, Yb and Gd can enhance its visible light absorption ability. In conclusion, the theoretical results agree with the experimental results and coincide with the external electronic orbital arrangement laws of rare earth elements in the periodic table, i.e., more f electrons give more impurity energy levels between valence band top and conduction band bottom. It is clear that RE/TiO₂ is more powerful than pure TiO₂ and should possess higher photocatalytic activity than pure TiO₂.

Key words: Rare earth doped TiO₂, Anatase, Density functional theory, Band structure