No abstract

To obtain highly efficient photocatalysts, we successfully prepared the GO/ZnO/CdS/Cu2S composite that possesses superior photocatalytic degradation performance via a three-step solvothermal process. A series of characterization techniques were used to verify the composition and performance of prepared samples, such as X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), Raman spectra, photoluminescence (PL) spectroscopy and so on. SEM reveals that copper ions are supported on the surface of CdS to form active sites for photocatalysis. Under the irradiation of ultraviolet (UV) and visible light, GO/ZnO/CdS/Cu2S photocatalyst exhibited relatively excellent photocatalytic degradation efficiency of methylene blue (MB), with 100% (80 min) and 95% (30 min), respectively. Compared with pure ZnO ([Formula: see text]) under the illumination of UV light, the kinetic constant of GO/ZnO/CdS/Cu2S catalyst is up to [Formula: see text], and as for visible light illumination, up to [Formula: see text], showing relatively excellent visible-light-induced photocatalytic activity. Besides, under UV and visible light, after three cycles of photodegradation, GO/ZnO/CdS/Cu2S still maintains the degradation efficiency of 78.3% and 74.8%, respectively, indicating that it has good stability. This work might inspire a new perspective that introduces the surface reaction sites (Cu2S) in the design of other graphene oxide/mental oxide-based heterojunctions for environmental purification.

The low-temperature hydrothermal and water bath methods are used to manufacture CuS@ZnO/CdS catalyst. The Rhodamine B degradation rate constant of CuS@ZnO/CdS is around 1.53×10-2 min-1, which is 3.9 times greater than that of ZnO. The coupling of CdS and loading of CuS onto ZnO surfaces were evaluated using XRD, SEM, TEM, and XPS. SEM demonstrated that 5 mg of CdS was the most effective in controlling the shape of ZnO nanoflakes. Ultraviolet-visible absorption (UV-Vis) and Photoluminescence (PL) spectra reveal that CdS and CuS decreased the bandgap of ZnO and boosted its ability to absorb visible light. Transient photocurrent response (TPR) and electrochemical impedance spectra (EIS) display that CdS and CuS facilitate the quick separation of photoexcited carriers in ZnO. Notably, the optimal weight ratio of CuS was determined to be 15%, since excessive amounts of CuS would operate as recombination centers and cover active sites. Additionally, the dual Z-scheme carriers movement mechanism was proposed using sacrificed agent experiments. In this study, CuS@ZnO/CdS photocatalyst degraded RhB nearly 99% in 80 min, which is superior to the earlier photocatalysts. Therefore, this article holds great significance in practical application of metal chalcogenide-modified ZnO-based photocatalysts with superior visible-light-induced degradation performance in environmental purification.