Abstract: The thin films of TiO₂, ZnO, Fe₂O₃ and heterojunction thin films of ZnO/TiO₂, Fe₂O₃/TiO₂ were prepared on quartz glass by dip-coating technique. The photocatalytic degradation of methylene blue on these films(λ=254 nm) showed that the photocatalytic activities of three films were in the following sequence: TiO₂>ZnO>Fe₂O₃, TiO₂/ZnO>TiO₂>TiO₂/Fe₂O₃. Compared with the films of pure ZnO and Fe₂O₃, heterojunction films of ZnO/TiO₂ and Fe₂O₃/TiO₂ had smaller contact angles, while Fe₂O₃/TiO₂ film showed super-hydrophilic property. To explain this result, a model of heterojunction band of Fe₂O₃/TiO₂, TiO₂/Fe₂O₃ and ZnO/TiO₂, TiO₂/ZnO were set up. The heterojunction band formed between the two seminconductors interface changed the transfer process of photogenerated electron-hole. Time-resolved photoconductivity spectra and Auger electron spectra results approved this explanation.

Key words: Heterojunction, Photocatalysis, TiO₂, Photoinduced hydrophilicity