Figure 4.

(a) The photocatalytic activity of TiO₂–Fe₂O₃ bilayer IOs depends on the TiO₂ and Fe₂O₃ coating thicknesses and the template size due to the alignment of the PSB with the semiconductor band gap to utilize the slow photon effect for performance enhancement. Each sample was measured three times. (b) Schematic drawing of the band structure and charge carrier movement in TiO₂–Fe₂O₃ bilayer IOs. Based on the type II heterojunction, photogenerated holes inside the valence band (VB) migrate toward the Fe₂O₃ layers and can induce an oxidation reaction at the catalyst’s surface. Electrons in the conduction band (CB) either get inside the TiO₂ layer or are scavenged by H₂O₂, which is added to the reaction solution.