Effect of surface doping of TiO2 powders with Fe ions on the structural, optical and photocatalytic properties of anatase and rutile

The effect of surface Fe-doping on the structural, photocatalytic, optical properties of polydisperse anatase and rutile TiO2 has been comprehensively studied. The TiO2 surface has been modified by Fe3+ ions through the adsorption from the diluted FeCl3 aqueous solutions. The prepared powders were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis, temperature programmed desorption techniques (TPD), Raman and UV–vis spectroscopy. With the adsorption isotherms of Fe3+ ions from FeCl3 aqueous solutions, it was found that adsorption of Fe3+ ions on the anatase surface is twice more efficient compared to that one on the rutile. The XRD and Raman spectroscopy measurements confirmed the monophase structure of the Fe-doped TiO2 with a subtle change in the lattice parameters and O/Ti ratio compared to the undoped counterparts. The red shift of the UV absorption edge has been registered for the Fe-doped anatase resulting in a significant decrease of its bandgap from 3.2 to 2.7 eV. The photocatalytic destruction of organic dye Safranin T over the prepared Fe-doped TiO2 under UV irradiation has been investigated. The influence of various energetically nonequivalent active sites on the surfaces of anatase and rutile on their photoactivity is considered.