Hierarchical Ag2O-ZnO-Fe3O4 composites with enhanced visible-light photocatalytic activity

Efficient visible-light-driven Ag2O-ZnO-Fe3O4 photocatalysts with hierarchical structures are synthesized. The as-prepared products are characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectra (DRS). XRD and XPS confirm the presence of Ag2O. DRS reveals that the adsorption edge of the Ag2O-ZnO-Fe3O4 photocatalysts is redshifted as compared with that of the ZnO-Fe3O4. Visible-light photocatalytic experiments are also conducted. By coupling with Ag2O, ZnO became responsive to visible light. The results show that the photocatalytic activity of the products is closely related to the mass ratio of Ag2O and ZnO, which is tunable and controlled by the amount of AgNO3 added during the fabrication process. The highest photocatalytic activity of the Ag2O-ZnO-Fe3O4 composites is achieved by adding 1.2 mol of AgNO3. The enhancement of photocatalytic activity can be attributed to the inhibition of electron-hole recombination. Furthermore, the as-prepared products can be easily attracted by an external magnetic field, which makes the composites recyclable. (C) 2015 Elsevier B.V. All rights reserved.