Photocatalytic activity of ZnO/graphene core-shell structure and its mechanism study

The ZnO@RGO quasi-core-shell composite photocatalyst, where ZnO nanoparticles (NPs) were wrapped by graphene nanoshells, was prepared via a one-step method. Photocatalytic experiments indicated that the photodegradation efficiency of ZnO@RGO on methylene blue (MB) increased by about 10 times compared to that of ZnO NPs. ZnO nanocrystals with the particle size of about 6 nm wrapped by RGO (reduced graphene oxide) nanosheets could be observed in transmission electron microscopy (TEM) images. X-ray diffraction (XRD) patterns showed that the structure of ZnO was hexagonal wurtzite. X-ray photoelectron spectroscopy (XPS) and Raman scattering manifested that there was strong interfacial interaction between ZnO and graphene which introduced about 3% interfacial stress and quantities of oxygen vacancies(VO). Photoluminescence (PL) further evidenced the approximately 80% decrease in band-gap emission intensity in ZnO@RGO compared with that in ZnO and the presence of interfacial VO. Finally, the mechanism of the enhanced photocatalytic activity in ZnO@RGO was proposed. The effective synergetic capture of graphene nanoshells and VO as a result of interfacial strain interaction improves the photocatalytic activities of ZnO based semiconductor photocatalysts.