TiO2/Sepiolite nanocomposites doped with rare earth ions: Preparation, characterization and visible light photocatalytic activity

摘要

Several rare earth (RE)-doped TiO2/Sepiolite (RE-TiO2/Sep) photocatalysts were prepared via microwave-hydrothermal treatment using six different types of RE ions: La, Ce, Pr, Nd, Eu or Gd. The obtained nanocomposites were characterized by using BET, XPS, PL and UV-vis techniques. The results revealed that the structures and chemical properties of the nanocomposites were significantly dependent on the radius of the Re3+. Since the radius of Re is much larger than that of Ti4+, Ti4+ could replace Re3+ in the lattice of RE2O3 in the form of Ti (3+) state and create a charge imbalance due to their smaller ionic radii. Correspondingly, for charge balance, more OH - will be adsorbed. The unoccupied 4f level of RE acts as a scavenger for photogenerated electrons, while surface adsorbed (OH)(- )acts as a hole trap, separating the photogenerated electron-hole pairs effectively. Eu-TiO2/Sep nanocomposite showed the best photocatalytic activity among all the RE-doped nanocomposites studied. The enhanced visible-light activity is mainly attributed to the enhanced separation of photoinduced carriers, low band gap energy, strong visible light absorption, high adsorption capacity and uniform distribution of titania nanoparticles on sepiolite as support.