Controlled preparation of superparamagnetic Fe3O4@SiO2@ZnO-Au core-shell photocatalyst with superior activity: RhB degradation and working mechanism

The designed synthesis of advanced ZnO heterostructures in a simple and mild way is of great significance, for the purpose of improving their photocatalytic performance and large-scale applications. Herein, a magnetic hierarchical microsphere Fe3O4@SiO2@ZnO@Au (FSZA) was successfully synthesized by multistep chemical methods, in which magnetic Fe3O4@SiO2 as core for the growth of ZnO nanorod-layer using microwave-assisted approach, followed by the functionalization of Au nanoparticles (NPs). Four FSZA microspheres (FSZA1, FSZA2, FSZA3, FSZA4) were controlled prepared by adjusting the concentration of the Au precursor for comparison. The as prepared products were characterized SEM, TEM, XRD, VSM, N-2-sorption, photocurrent and XPS techniques. The results revealed that the as-synthesized microspheres have a good monodispersity, uniform core-shell structure and high magnetization. The photocatalytic test indicated the FSZA3 product possessed the best activity among all tested products, and the photodegradation rate of rhodamine B (RhB) reached 93.54% after UV irradiation of 80 min. The enhanced activity of FSZA3 was ascribed two major contributions, which were the larger specific surface area and the improved separation efficiency of the photogenerated carriers. The decomposition mechanism was discussed in detail. Additionally, such integrated FSZA3 photocatalyst was easily recovered by a magnet, which was reused at least five times without any appreciable reduction in photocatalytic efficiency. (C) 2017 Elsevier B.V. All rights reserved.