Reduced Graphene Oxide / Zinc Oxide / Silver Nanocomposites Trigger Visible Light Activity for Efficient Photocatalytic Degradation of Xylenol Orange as a Persistent Pollutant Model

The use of heterojunctions in photocatalysis captures solar energy better, improving charge separation and transfer, thus enhancing photocatalytic activity and stability. This approach has the potential to alleviate energy and environmental challenges. In this study, metal oxide (i.e., ZnO NPs) and metal/metal oxide junctions (i.e., ZnO/Ag NPs) nanostructures were investigated. Two nanohybrids, labeled as ZnO-rGO and ZnO/Ag-rGO, were chemically prepared through a low-temperature wet chemical route. The physicochemical properties were altered by the presence of graphene in the prepared metal oxide and metal/metal oxide nanohybrids, as elaborated by the Brunauer–Emmett–Teller (BET) surface area, transmission electron microscope (TEM), X-ray diffraction (XRD), UV–visible absorption spectra, dynamic light scattering (DLS), and zeta potential techniques. In addition, photocatalytic performance was investigated through several parameters such as the effect of contact time, pH, catalyst, and dye concentrations, respectively. The results obtained indicated a remarkable increase in photodegradation efficiency upon the addition of graphene to metal and metal/metal oxide heterojunction nanostructures, with an efficiency ranging from 88 to 90% within 180 minutes compared to their pristine individual components.