Liquid phase-based ultrasonic-assisted synthesis of G–ZnO nanocomposites and its sunlight photocatalytic activity

The graphene (G)–ZnO (G–ZnO) nanocomposites with high photocatalytic activity have been successfully prepared by a simple and inexpensive liquid phase-based ultrasonic-assisted method with different doping amounts of graphene oxide . The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy , UV–visible diffuse reflectance spectroscopy (UV–vis/DRS) and Brunauer–Emmett–Teller (BET) analysis. The results indicate that the assistance of ultrasonic can effectively decrease the size of ZnO nanostructure and increase the uniformity of the mixture of graphene and ZnO particles. Meanwhile, the sunlight absorption of the G–ZnO nanocomposite is gradually improving with the increase of the ratio of graphene. The obtained G–ZnO-30 photocatalyst shows the best photocatalytic activity for methylene blue (MB) and methyl orange (MO) under sunlight irradiation. The degradation rates of MB and MO in the presence of G–ZnO-30 reached up to 98.1% and 95.7%, respectively, under solar radiation for 1   h and 6   h. In addition, the photocatalyst exhibits outstanding separability and high stability.