Zinc Oxide with Visible Light Photocatalytic Activity Originated from Oxygen Vacancy Defects

Abstract

In this study, ZnO material with oxygen defect was successfully synthesized using a hydrothermal method and interestingly, it was found to possess a remarkable photocatalytic activity under the visible light irradiation. The synthesized ZnO material was then characterized using X-ray diffraction (XRD), diffuse reflectance ultraviolet-visible (DR UV-vis), Fourier transform infrared spectroscopy (FTIR), and spectrofluorometer. Both diffraction pattern and absorption spectrum showed the characteristic of ZnO. However, the maximum emission wavelength of the synthesized ZnO was observed at 558 nm, showing that the ZnO was formed with a high concentration of oxygen vacancy. The excitation spectra also indicated that the prepared ZnO could be excited at the visible light region, which was more than 400 nm. The ZnO was evaluated for photocatalytic phenol degradation under UV and visible light. After 15 hours-reaction, the synthesized ZnO showed the ability to degrade 59.8% phenol under UV light and 39.6% phenol under visible light. This result showed a remarkable performance of ZnO under visible light, which was comparable to that performed under UV light. This study proposed that the existence of oxygen vacancy defects successfully induced the photocatalytic activity of ZnO under visible light irradiation through the electron trapping mechanism in the oxygen vacancy state.