Hydrothermal synthesis of Z-type SnO₂ quantum dot-modified ZnO nanosheets with enhanced photocatalytic activity

SnO₂ quantum dots, ranging from 10 to 30%, were combined with ZnO nanosheets to create a heterojunction photocatalyst. This composite was generated using a basic hydrothermal method, which was then followed by high-temperature calcination to enhance the photocatalytic activity of ZnO. The results showed that the synthesized SnO₂ nanoparticles with tetragonal rutile phase and ZnO nanosheets with hexagonal fibrillar zincite phase, the coupling of SnO₂ quantum dots and ZnO nanosheets improved the separation efficiency of the photogenerated carriers, and at the same time broadened the photoresponse range. Through the degradation of the organic dye Rhodamine B (RhB), the best photocatalytic activity was found at 20% amount of SnO₂ in the composite sample (SZ-2), and the degradation efficiency of RhB reached 96.5% at the light irradiation time of 100 min. In addition, an in-depth study of the photocatalytic mechanism of the constructed heterojunction by active group trapping experiments, and the results showed that •O₂⁻ and h⁺ were the main active substances in this degradation system. Meanwhile, the SZ-2 photocatalyst was tested for five cycles, and the degradation efficiency of the 5th cycle was 72%. The cycle test indicates that the SZ-2 sample is highly stable and reusable. Therefore, the results showed that the prepared SnO₂/ZnO heterojunction photocatalysts are suitable materials for degrading organic dyes.