Investigation on synergistic effect of rGO and carbon quantum dots-embedded ZnO hollow spheres for improved photocatalytic aqueous pollutant removal process

A series of ternary ZnO hollow sphere/carbon quantum dots/reduced graphene oxide (ZnO/CQDs/r-GO) nanocomposites were successfully prepared via solvothermal technique in the presence of the polyethylene glycol 400 (PEG 400) as a solvent. The structural details of as-prepared ZnO/CQDs/r-GO nanocomposites were characterized by powder X-ray diffraction analysis. The morphological properties of the composite were analyzed using field emission scanning microscopy (FE-SEM). The visible light absorption ability of the as-prepared pristine and ternary nanocomposites was examined using UV–visible (UV–Vis) spectrophotometry. The photocatalytic activity of ZnO, ZnO/CQDs, ZnO/r-GO, and ZnO/CQDs/r-GO nanostructures were evaluated for the degradation of organic pollutants such as methylene orange (MO), rhodamine B (RhB), and methylene blue (MB). The different composites with various amounts of reduced graphene oxide (r-GO) and carbon quantum dots (CQDs) were synthesized to enhance photocatalytic activity. The ZnO/CQDs/r-GO composites showed excellent potential for photocurrent generation compared with ZnO, ZnO/CQDs and ZnO/r-GO under-stimulated sunlight. The effect of various parameters such as the effect of reaction temperature, catalyst concentration, pH, and concentration of MB dye has been also studied. The photo-assisted catalytic degradation properties of the catalyst after five cycles exhibit high stability.