异质结型光催化膜的活性及其机理研究

采用浸渍提拉法制得TiO₂,ZnO,Fe₂O₃,ZnO/TiO₂,TiO₂/ZnO,Fe₂O₃/TiO₂和TiO₂/Fe₂O₃石英玻璃基底负载膜.光催化降解亚甲基蓝实验表明,TiO₂和ZnO具有良好的光催化活性,Fe₂O₃活性较差.但形成异质结后,TiO₂和Fe₂O₃的光催化降解能力发生明显的变化.用254nm紫外光光照后,TiO₂,ZnO和Fe₂O₃等3种氧化物膜与水的接触角均有不同程度的降低,TiO₂表现出超亲水性,ZnO/TiO₂和Fe₂O₃/TiO₂膜与水的接触角小于对应的单纯ZnO和Fe₂O₃膜与水的接触角,其中Fe₂O₃/TiO₂表面出现超亲水性.瞬态光电导谱的少数载流子寿命的测定表明,异质结势垒电场能有效地增强光生电子-空穴对的分离效率.根据能带理论建立的两组异质结能带模型可合理地解释实验结果.

Photocatalytic Activity and Mechanism of Heterojunction Thin Films

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.