Facile fabrication of Fe-TiO₂ thin film and its photocatalytic activity

Fe³⁺-TiO₂ (Fe-TiO₂) thin films were successfully prepared using a "sandwich" approach. TiO₂ NPs were doped with different Fe³⁺ content (0.05%, 0.1%, 0.2% molar ratio), and the modified TiO₂ NPs were deposited on glass flat support by dip coating.Structural, morphological, optical, and photocatalytic properties of Fe-TiO₂ thin films were studied. XPS spectra confirm the presence of Ti, Fe, O, and defective -OH groups at the material surface. The Fe 2p spectrum demonstrates the existence of Fe³⁺. SEM images indicate that the incorporation of Fe³⁺ deforms in some degree the homogeneity of the TiO₂ system. Additionally, incorporation of Fe³⁺ ions to the network creates an impurity band near the VB due to the oxygen vacancies, resulting in the reduction of the effective optical band gap. Photocatalytic activity of fabricated thin films in the elimination of sulfamethoxazole (SMT) follows pseudo first-order kinetics. The highest SMT removal yields were achieved using the sample with 0.05%Fe. Additionally, the use of greater thicknesses improves the removal performance. However, material detachment limits the maximum usable value around 6 µm.Finally, stability and reusability of catalysts were confirmed studying the photocatalytic activity over three cycles and evaluating that no Fe³⁺ leaching occurred.