Doped TiO2 Nanotubes: Synthesis and Application

TiO2 nanotubes have recently been studied extensively due to their high surface areas and finite length scales, allowing highly efficiency electron-hole charge separation and reduced recombination. Owing to these properties they can be used for instance in photocatalysis and lithium-ion batteries. The preparation of TiO2 nanotubes through hydrothermal process has received much attention. However, the practical application of TiO2 nanotubes is significantly hindered by their intrinsic energy band gap > 3 eV, which ensures that these materials cannot be excited by visible light. Visible-lightactivated TiO2 can be prepared by doping through incorporation or decoration with other metal ions, non-metal ions, and semiconductors. This review discusses various types of dopants, doping methods, and applications of doped TiO2 nanotubes.