Doping and transformation mechanisms of Fe 3+ ions in Fe-doped TiO 2

A series of Fe-doped TiO2 samples with different concentrations of Fe3+ ions annealed at different temperatures were prepared using a sol–gel method. For Fe-doped TiO2, the existing states of Fe3+, the transformation of these existing states and the phase transition are investigated. It is revealed that the existing states of Fe3+ and the transformation of these existing states (substitutional Fe3+, α-Fe2O3 and Fe2TiO5) are closely related to the annealing temperature and the concentration of Fe3+. The anatase–rutile (A–R) transition is promoted by the substitutionally doped Fe in the TiO2 lattice. In addition, the Fe-doped TiO2 with a high calcination temperature (800 °C) and high doping concentration (x > 20) shows obvious ultrasonic piezoelectric catalytic activity for the reduction of CO2 to CH4. This work may be useful in understanding the doping mechanisms of Fe-doped TiO2, and the fabrication of new catalytic materials.