Influence of Fe-Doping on the Structural and Electronic Properties of the TiO₂ Anatase:Rutile

The Fe-doped anatase and rutile TiO2 phases were investigated by using a combined experimental and theoretical approach. The Fe-doped phases were characterized by X-ray diffraction with Rietveld refinement. The band structure and projected density of state (PDOS) were fully characterized using DFT/plane-wave calculations on a supercell model with 48 atoms. The band gaps of 3.17 and 2.95 eV were estimated for the pure anatase and rutile TiO2 phases. The band gap values decreased to 3.00 and 2.13 eV with Fe doping for anatase and rutile TiO2-Fe phases, respectively. The water-splitting reaction on the anatase (0 1 0) TiO2 and TiO2-Fe surfaces was investigated. The quantum efficiency assessed by the transfer rate of electrons and holes increased with the presence of Fe in the TiO2 structure. The initial steps of the reaction mechanism and the transition states were determined using the NEB (nudged elastic band) method considering the species involved H2O, OH center dot, and H+ on the (0 1 0) TiO2 surface. The activation energies of 0.29 and 0.08 eV were estimated for pure anatase TiO2 and anatase TiO2-Fe structures. The DFT/plane-wave calculations on the synthesized Fe-doped material are predicted to improve its photocatalytic properties toward water splitting.