Iron-Doped Titanium Dioxide Nanomaterials: Synthesis, Characterization and Photodegradation Catalytic Behavior

Titanium dioxide (TiO2) is a very good material for various photocatalytic industrial applications because of its non-toxicity, high chemical stability, low cost and relatively good photoactivity. However, one of the most serious challenges to its applicability is its wide band gap and because of that TiO2 absorbs mainly in the UV region of the solar spectrum, which corresponds to a small portion (<10%) of the sun's energy.

In this thesis, doping of TiO2 is employed as a method to improve TiO2 optical properties by decreasing the band gap and enabling the material to absorb a larger fraction of the visible spectrum. A series of iron-doped titanium dioxide nanoparticles containing various percentages of iron was prepared and their chemical, structural, optical and electrochemical properties were characterized. These results confirm that the proposed materials were successfully prepared and that they indeed have smaller band gaps.

Raman imaging was also employed to map the various phases present in our samples and to identify surface functionalities on the materials and their accessibility to binding especially with dyes, such as N3 and Z907 dye, for the first time. The results shows the coexistence of phases in TiO2 as well as adsorption pattern of the dyes on the surface of the TiO2.

Finally, The photodegradation of methylene blue has been studied to quantify the photocatalytic activity of all prepared iron-doped TiO2 and pure TiO2 photocatalysts under simulated sunlight. The measurements are performed at two pH values and the different mechanism observed can be explained in terms of changes in the materials potential of zero charge (PZC) and how surface charge affects the dye adsorption. Using the Langmuir-Hinshelwood model, rate constants (kobs) decreasing with an increase in the molar percentage of iron in TiO2 as well as a decrease in the materials band gap. This trend is opposite to what was expected and it could be due to a significant increase in the charge recombination rate when the band gap is reduced, meaning that less charge is available to participate in the photodegradation process.