Two methods for microwave irradiation synthesis of TiO₂–ZnO–graphene ternary hybrids with enhanced photocatalytic activity

In this study, graphene–zinc oxide–titanium dioxide (RGO–ZnO–TiO₂) ternary hybrids are successfully synthesized by two methods called 'one step' and 'two steps', by using a simple microwave treatment of a solution containing graphene oxide, ZnO, TiO₂, water and ethanol. Their morphology, structure, and photocatalytic performance in degradation of methylene blue, were characterized by scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffraction analysis, Fourier transform infrared and UV–vis analysis. The results show that RGO–ZnO–TiO₂ (GZT) hybrids (containing 7% graphene mass ratio) improve photodegradation efficiency 1.39- and 1.8-fold, compared with RGO–ZnO (GZT₀) (containing 7% graphene mass ratio) and pure ZnO, because of reduction of electron–hole recombination in ZnO due to introduction of TiO₂. Furthermore, we found that the photocatalytic activity in the 'one step' method is higher than in 'two steps'. (paper)