Synthesis of ZnS/CuS nanospheres loaded on reduced graphene oxide as high-performance photocatalysts under simulated sunlight irradiation

A series of ZnS/CuS nanospheres decorated on reduced graphene oxide (rGO) nanocomposites (ZnS/CuS-rGO) as high-efficiency photocatalysts have been successfully fabricated through a facile solvothermal approach combined with a cation exchange method. Graphene oxide (GO) is utilized as a precursor and a substrate, and reduced into rGO simultaneously with the formation of ZnS-rGO during the solvothermal process. The photocatalytic activities of the as-prepared nanocomposites have been evaluated by the photocatalytic degradation of different model organic pollutants, such as eosin B (EB), methylene blue (MB), rhodamine B (RhB), methyl orange (MO) and malachite green (MG), in the presence of hydrogen peroxide (H₂O₂) under simulated sunlight irradiation. The results demonstrate that ZnS/CuS-rGO nanocomposites exhibit improved photocatalytic performance which is higher than that of bare ZnS and ZnS/CuS nanospheres, and nanocomposites with a theoretical graphene weight ratio of 5 wt% (ZC-5% rGO) have the highest photocatalytic activity. Specifically, ZC-5% rGO is capable of eliminating 99.22% of dye pollutants in an EB and MB mixed solution after exposure to light irradiation for only 60 min. In addition, it exhibits no decrease in photocatalytic efficiency for the elimination of individual EB and MB after recycling for five times. Finally, an appropriate photocatalytic reaction mechanism has also been proposed and elucidated to explain the excellent performance of ZnS/CuS-rGO nanocomposites.