Photocatalytic activity of hierarchically structured TiO₂ films synthesized by chemical vapor deposition

Hierarchically structured TiO₂ photocatalyst films were synthesized using low-pressure metal-organic chemical vapor deposition (LPMOCVD) method to examine their photocatalytic activity. The thickness of the TiO ₂ films increased proportionally with increasing deposition time. The TiO₂ film synthesized at 773 K showed a hierarchical structure composed of vertically grown laminar (112)-oriented anatase crystals. With increasing deposition time, the grain became larger and the morphology became sharper. In the initial CVD stage, small particular crystals were formed, above which sequential growth of layers of columnars with increasing size took place, forming hierarchical structure. The hierarchically structured TiO₂ film exhibited much higher photocatalytic activity than unhierarchically structured TiO₂ film. The photocatalytic activity increased with increasing film thickness.