Synthesis, structure and photocatalytic properties of Fe(III)-doped TiO2 prepared from TiCl3

Iron(III)-doped titanium dioxide photocatalysts were prepared from aqueous titanium(III) chloride solution in the presence of dissolved FeCl3 (0–10.0 at.% relative to TiCl3) by co-precipitation method. The precipitate was completely oxidized in the aerated suspension, hydrothermally treated, washed and calcinated. The structure of the powders was characterized by thermoanalysis (TG-DTA), diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), nitrogen adsorption and transmission electron microscopy (TEM). The light absorption of the iron-containing powders is red shifted relative to the bare sample. The particle size and anatase content were found to significantly decrease at iron contents ≥6.0 at.% which is accompanied with the increase of their specific surface area. XANES measurements showed that the local structure of iron systematically changes with the variation of the dopant concentrations: at higher Fe-contents, hematite- or goethite-like environments were observed, consistent with the formation of separate X-ray amorphous Fe(III)-containing phases. The local structure of iron gradually transformed with decreasing dopant concentrations, possibly due to substitution of Fe(III) in the titania (TiO2) crystal lattice. Energy dispersive X-ray analysis (EDX) and chemical analysis was used to characterize the iron content of the samples in the bulk and X-ray photoelectron spectroscopy (XPS) in the surface layer of the particles. The photocatalytic performance of the prepared photocatalysts was compared with the activity of Aldrich anatase under UV–vis and VIS irradiation in two different photoreactors. Maximum photocatalytic performance was found at 3.0 at.% iron concentration for UV–vis and at 1.2 at.% for VIS irradiation. Doping with iron(III) ions increased the photodegradation rate of phenol by a factor of three for UV–vis irradiation and by a factor of two for VIS irradiation, relative to the bare photocatalyst.