Oxygen-vacancy-tunable mesocrystalline ZnO twin "cakes" heterostructured with CdS and Cu nanoparticles for efficiently photodegrading sulfamethoxazole

Understanding and designing excellent photocatalysts is crucial to incorporate them into pollutant-elimination application and has been highly concerned. In the present work, we have prepared twin-cake-like ZnO mesocrystals with tunable oxygen vacancies (OVs) by using Arabic gum as green agent, and then decorated CdS and Cu nanoparticles (NPs) on their surface to form Cu/CdS/ZnO-OVs heterostructured photocatalysts. The photodegradation performance and mechanism of the photocatalysts was elucidated through degrading sulfamethoxazole (SMX) by using simulated sunlight as the light source. It is revealed that the OVs-engineered ZnO twin "cakes" (optimal ZnO-OV3) exhibit obviously enhanced photocatalysis than normal ZnO particles synthesized without Arabic gum, which can be explained due to the improved visible-light absorption and photocarrier separation by OVs. Moreover, the decoration of CdS and/or Cu NPs onto ZnO-OV3 offers a further enhancement to the photocatalysis; particularly the ternary composite 7%Cu@20%CdS@ZnO-OV3 manifests the highest photodegradation performance, which is improved by 1.64 and 9.66 times over that of single ZnO-OV3 and CdS, respectively. This phenomenon originates from the improved separation of photocarriers by the CdS/ZnO-OV3 and Cu/ZnO-OV3 interface fields. Experiments and theories were combined to deeply study the underlying photocatalysis mechanism as well as the decomposition behavior of SMX.