A facile one-step approach to synthesizing ZnO/graphene composites for enhanced degradation of methylene blue under visible light

A series of visible light-responsive ZnO/graphene composite photocatalysts were successfully synthesized by a facile single step solvothermal method, using ethylene glycol as a solvent and a reducing agent. Successful deposition of wurtzite ZnO nanoparticles onto the graphene was confirmed by high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). UV–vis diffuse reflectance spectroscopy (DRS) showed that the as-prepared ZnO/graphene composite photocatalysts had enhanced visible light absorption and also exhibited a red-shift of the band-edge as compared with the pure ZnO. Fluorescence emission spectra showed that ZnO/graphene composites caused improved charge separation when compared with the pure ZnO. The photocatalysis experiment demonstrated that graphene has an important role in the enhancement of photocatalytic performance and the ZG-4 composite attained a maximum degradation efficiency of almost 100% under visible light irradiation for 90 min as compared with pure ZnO (58%). The enhancement in photocatalytic activity is likely to be due to the synergistic effect of improved adsorptivity of dyes, enhanced visible light absorption and effective charge separation.