Recent advances in Ti3+ self-doped nanostructured TiO2 visible light photocatalysts for environmental and energy applications

Defect of semiconductor is a double-edged sword, which is of great importance for improving the photocatalytic performance and should be controlled rationally. Ti3+ defects lead to some interstitial states, which extend the light response to visible-near infrared light, and promote the separation of photogenerated electron-hole (e−-h+) pairs obviously. Although the photocatalytic mechanism for Ti3+ defects is still controversial at present, the obvious promoted effect for various TiO2 nanomaterials is remarkable. In this review, we mainly summarize the controllable synthesis of zero, one, two and three-dimensional (0D, 1D, 2D and 3D) Ti3+-TiO2 based materials, including 0D nanoparticles, 1D nanotubes/nanobelts/nanowires, 2D nanosheets, 3D nanospheres, etc. The visible-light-driven photocatalytic mechanism of Ti3+-TiO2 is summarized. Finally, the influence of Ti3+ defects for the application of TiO2 photocatalysts in fields of both environment and energy is also reviewed.