Seed-mediated synthesis and the photo-degradation activity of ZnO–graphene hybrids excluding the influence of dye adsorption

The nano-sized ZnO–graphene hybrid has been prepared through combining the facile sol–gel process and hydrothermal method by using Zn(NO3)2·6H2O and hexamethylenetetramine (HMT) as growing reactants in the presence of ZnO–graphene oxide (ZnO–GO) seeds. The obtained products have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and UV–vis absorption spectroscopy. The results show that the GO has been converted to reduced-graphene oxide during the hydrothermal process due to the released reductant from HMT. The photo-degradation of methylene blue in the presence of ZnO–graphene (excluding the influence of the dye adsorption on the catalyst) has also been investigated in detail. It is found that the preparation conditions have significant effects on photo-catalytic properties of the composites, and that ZnO–graphene prepared in the optimal conditions exhibits the optimum activity. This facile and low-cost method will make the composite a perfect candidate in applications of photo-catalysis and other areas.