异质结型光催化膜的活性及其机理研究

Photocatalytic Activity and Mechanism of Heterojunction Thin Films

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.

The thin films of TiO_2, ZnO, Fe_2O_3 and heterojunction thin films of ZnO/TiO_2, Fe_2O_3/TiO_2 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: TiO_2>ZnO>Fe_2O_3, TiO_2/ZnO>TiO_2>TiO_2/Fe_2O_3. Compared with the films of pure ZnO and Fe_2O_3, heterojunction films of ZnO/TiO_2 and Fe_2O_3/TiO_2 had smaller contact angles, while Fe_2O_3/TiO_2 film showed super-hydrophilic property. To explain this result, a model of heterojunction band of Fe_2O_3/TiO_2, TiO_2/Fe_2O_3 and ZnO/TiO_2, TiO_2/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.