Oxygen-defected ZnO: Facial Synthesis and high photocatalytic performance under visible light

Abstract

The current study describes the main morphological and the photocatalytic performance differences between three zinc oxide samples; commercially available, synthetized tetrapods, and synthetized oxygen-defected sample. Oxygen-defected ZnO particles were prepared through a novel one-step thermal heating of metallic zinc powder at 1000 °C in a small concentration of oxygen gas. On the other hand, the tetrapods ZnO sample was prepared under the same conditions but in a high concentration of oxygen gas. The three materials were characterized by XRD, Raman spectroscopy, SEM, EDX, DRspectroscopy and finally EPR. The oxygen-defected sample has a grey colour and it tends to have a distorted tetrapods structure with a multitude of defect surface VO-Zn2-x sites. Moreover, the absorption spectrum of the oxygen-defected sample showed a red-shift towards a visible light region as compared to that of commercial sample, with a calculated bandgap of 3.07 eV. The photocatalytic performance of the three materials was evaluated in the liquid phase decolourization of methyl green under the illumination of black UV light at 375 ± 10 nm and visible light 425 ± 20 nm. A high photocatalytic activity was observed for the oxygen-defected ZnO material under visible light illumination compared to the other two materials.