Correlation of Physicochemical Properties with the Catalytic Performance of Fe-Doped Titanium Dioxide Powders

A simple method for synthesis of Fe-doped TiO₂ nanocrystalline powders, namely by coprecipitation, is described in this study. The influence of the iron content on the structural, morphological, optical and photocatalytic properties is determined. On the basis of XRD analysis, it was observed that anatase crystalline phase of TiO₂ was stabilized, and the deformation of the elemental cell and strain increase with increasing of iron content due to the substitution of Ti⁴⁺ with Fe³⁺. The substitution process and the interaction between titanium and iron ions was also confirmed from the shifting of the Raman fundamental vibration from 144 to 149 cm^-1. The absorption spectra showed that the optical response of TiO₂ was red-shifted and the optical energy band gap decreased in the case of low content of Fe, whereas at high content of iron (in this case 3.11%), the optical response is blue-shifted due to the quantum size effect. The photocatalytic performance of Fe-doped TiO₂ materials was correlated with the optical energy band gap. Thus, the best photocatalytic performance was obtained for the sample that contains 1.48% iron because it displays the lowest energy band gap (2.79 eV), so the material can absorb radiation from the visible range, even if this sample presents the lowest surface area. The efficiency of the degradation of Methylene Blue dye, under exposure to low intensity ultraviolet and visible radiations was 39%. Based on the characterization and performance of the Fe-doped TiO₂ materials, it was concluded that the optimal iron content for our studies was 1.48%.