State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
ACS Appl Mater Interfaces. 2011 Aug;3(8):3152-6. doi: 10.1021/am200655h. Epub 2011 Jul 28.
Different composite films prepared by coupling ZnO and nitrogen-doped ZnO (N-ZnO) were used to photodegrade humic acids (HA). The catalysts exhibit an activity in the order of glass/ZnO/N-ZnO > glass/N-ZnO >glass/ZnO > glass/N-ZnO/ZnO when light is irradiated from the film to glass substrate. However, glass/ZnO/N-ZnO exhibits a lower activity than glass/N-ZnO/ZnO when light is illuminated from glass to film. Moreover, glass/ZnO/N-ZnO shows a lower activity when light is irradiated from glass to film than that irradiated in the opposite direction. These results suggest that it is not always the case that the presence of a heterojunction at interface of two semiconductors can definitely result in improving the photoactivity of the heterostructure although it can suppress the recombination of photogenerated charge carriers. They also indicate that photodegradation of HA is mainly via the oxidization by HO• (rather than directly by O(2)(-) and h(+)), which is produced mainly by the reactions with h(+). This implies the importance of fabrication a right heterojunction at the interface between the composite materials when they are used for photocatalysis. We envision that this work will help to develop new photocatalysts, as well as to understand better the photocatalytic mechanism.
不同的复合膜通过耦合 ZnO 和氮掺杂 ZnO（N-ZnO）制备，用于光降解腐殖酸（HA）。当光从膜照射到玻璃基底时，催化剂的活性顺序为玻璃/ZnO/N-ZnO>玻璃/N-ZnO>玻璃/ZnO>玻璃/N-ZnO/ZnO。然而，当光从玻璃照射到膜时，玻璃/ZnO/N-ZnO 的活性低于玻璃/N-ZnO/ZnO。此外，当光从玻璃照射到膜时，玻璃/ZnO/N-ZnO 的活性低于相反方向照射的活性。这些结果表明，尽管异质结可以抑制光生载流子的复合，但在两种半导体的界面处存在异质结并不一定能提高异质结构的光活性。它们还表明，HA 的光降解主要是通过 HO•（而不是直接通过 O(2)(-)和 h(+)）氧化，这主要是通过与 h(+)的反应产生的。这意味着在将复合材料用于光催化时，在界面处制造正确的异质结非常重要。我们预计这项工作将有助于开发新型光催化剂，并更好地理解光催化机制。
