Effect of Ag shapes and surface compositions on the photocatalytic performance of Ag/ZnO nanorods

Photoreduction and hydrothermal methods were used respectively to prepare Ag surface modified ZnO nanorods in this paper. The surface microstructure and photocatalytic performance of Ag/ZnO nanorods for methyl orange degradation were evaluated in detail. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis. diffuse reflectance spectroscopy (DRS) were used for microstructure analysis of as-prepared Ag/ZnO nanorods. FESEM images showed that Ag presented nanosheets in Ag/ZnO sample (AZP) prepared by photoreduction method, while it exhibited nanoparticles in the sample (AZH) using hydrothermal method. DRS studies clearly displayed surface plasmon resonance (SPR) effect of Ag in AZH samples. Furthermore, there was a red shift on absorption edge for AZH samples compared with bare ZnO and AZP samples. The XPS results revealed that Ag+ ions existed on the surface of AZH samples. In contrast to AZH sample, AZP sample demonstrated the higher photocatalytic activity under UV-Vis. light illumination. However, it was interesting that AZH samples exhibited the visible-light-driven photocatalytic activity, which may be due to the cooperation role of the existence of Ag+ ions and SPR effect of Ag nanoparticles. All these results illustrated that the shapes and surface compositions of Ag may be important factors that influence the photocatalytic performance of Ag/ZnO nanorods. The surface microstructure related photocatalytic mechanism was finally proposed. (C) 2014 Elsevier B.V. All rights reserved.