Synthesis of a ZnO/CdS/TiO₂ composite with enhanced photocatalytic activity and stability by a simple solution-based method

A simple, low-cost synthetic approach was developed for fabricating a TiO₂ layer on the surface of CdS-sensi-tized ZnO nanorods by a liquid-phase deposition method. In the ZnO/CdS/TiO₂ composite structure, CdS quantum dots are grown on ZnO nanorods and the resulting CdS/ZnO nanorods are uniformly coated with a TiO₂ layer. UV/Vis absorption spectroscopy showed that CdS could provide better light-harvesting ability, and the photocatalytic activity was significantly im-proved by CdS compared with that of ZnO nanorods alone. Recycling experiments on ZnO/CdS showed continuous attenuation of photocatalytic performance, whereas the TiO₂ protective layer maintains superior photocatalytic performance of the photocatalyst and strongly inhibits the photocorrosion of CdS. In addition, a possible photocatalytic mechanism of the ZnO/ CdS/TiO₂ composite is proposed.