Investigation of the Effect of Oxide Additives on the Band Gap and Photocatalytic Efficiency of TiO2 as a Fixed Film

The effects of various additives (Y₂O₃, Ga₂O₃, and WO₃) on photocatalytic degradation efficiency under UV light-emitting diodes (LEDs) and the optical properties of TiO₂ Degussa P25 were investigated using ketoprofen and diclofenac, two non-steroidal anti-inflammatory drugs commonly detected in German rivers. Experimental results demonstrated that thin films containing these additives exhibited similar photocatalytic degradation efficiencies as pure TiO₂, achieving a 30% degradation of ketoprofen over 150 min. In contrast, the Y₂O₃/TiO₂ thin film showed significantly improved performance, achieving a 46% degradation of ketoprofen in 180 min. Notably, the Y₂O₃/TiO₂ system was three times more effective in degrading diclofenac compared to pure TiO₂. Additionally, the Y₂O₃/TiO₂ photocatalyst retained its activity over three successive cycles with only a slight decrease in efficiency. The photocatalytic degradation of both organic pollutants followed first-order kinetics with all photocatalysts. The investigation included SEM imaging to assess the surface homogeneity of the thin films and UV-vis solid-state spectroscopy to evaluate the impact of the additives on the energy band gap of TiO₂.