Figure 5.

(a) The mean photocatalytic activity of TiO₂–Fe₂O₃–TiO₂ multilayer IOs after three measurements depends on the composition and template size but shows a significant standard deviation. (b) The individual activities during seven consecutive measurements of 16 nm TiO₂–2 nm Fe₂O₃–2 nm TiO₂ and 16 nm TiO₂–4 nm Fe₂O₃–2 nm TiO₂ multilayer IOs for the 252 nm template increase during the first four measurements, slightly decrease in the following two measurements and are stable afterward. (c) The band structure of TiO₂–Fe₂O₃–TiO₂ multilayer IOs depicts trapping of photogenerated holes inside the Fe₂O₃ layers due to adding another TiO₂ layer. Electrons in the CB move toward the TiO₂ layers, and those located in the outer layers can induce reductive reactions in the surrounding electrolyte or get scavenged by H₂O₂ molecules. (d) XRD patterns show anatase TiO₂ peaks for Fe₂O₃ functionalized TiO₂ IOs after photocatalysis measurements. Multilayer structures exhibit significantly higher peak intensities, indicating that this composition provokes photoinduced crystallization of the TiO₂ layers.