One-step pyrolytic synthesis of ZnO nanorods with enhanced photocatalytic activity and high photostability under visible light and UV light irradiation

Abstract

Zinc oxide (ZnO) nanostructures with different morphologies, including nanorods, nanospheres and nanosheets, were prepared by a simple, one-step method via the pyrolysis of zinc acetate, zinc oxalate and zinc nitrate, respectively. The as-prepared ZnO nanostructures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–visible diffuse reflectance spectroscopy (DRS). The photocatalytic activities of the ZnO nanostructures were evaluated by the photodegradation of two typical organic dyes, rhodamine B (RhB) and methyl orange (MO). It was found that the ZnO nanorods exhibited the highest photocatalytic activity among the three ZnO nanostructures under both visible light and UV–visible light irradiation. Furthermore, the ZnO nanorods photocatalyst also showed excellent photostability and reusability under visible and UV–visible light irradiation. In addition, mechanism studies by using active species trapping experiments suggested that hydroxyl radicals (OH), photoinduced holes (h+) and superoxide anion radicals (O2−) were involved in the photocatalytic process. The O2− played a major role under visible light irradiation, whereas the OH was the main active species under UV light irradiation. A possible mechanism for the charge separation and organic dye pollutants degradation was proposed.