Enhanced photocatalytic performance of hollow spherical CdS QDs@ZrO2–TiO2 composites with double Z-scheme heterostructures

In this paper, CdS QDs@ZrO2–TiO2 hollow spherical composites with double Z-scheme heterostructure modified by CdS QDs were prepared by the sol–gel method and vacuum impregnation method using polystyrene (PS) microspheres synthesized by the self-assembly technique as templates. A series of characterization results show that CdS QDs@ZrO2–TiO2 composites treated by PS microspheres have the structure of hollow spheres with uniform size and orderly arrangement. Moreover, the double Z-scheme heterojunction formed between CdS QDs, ZrO2, and TiO2 in the composite can optimize the charge transfer path and improve the charge separation efficiency. Results of the photodegradation and the photo-splitting water of CdS QDs@ZrO2–TiO2 composites show that, compared with other systems, CdS QDs@ZrO2–TiO2 composites have the highest photocatalytic degradation rate of crystal violet, and meanwhile, the photocatalytic hydrogen production rate of the composite under simulated sunlight is more than 100 times that of TiO2. The good absorption of visible light, the successful construction of double Z-scheme heterojunction, and the unique hollow sphere structure of CdS QDs@ZrO2–TiO2 composites are the key factors for enhanced photocatalytic performance.