Photocatalytic activity of Cd1−xZnxS/K2Ti4O9 for Rhodamine B degradation under visible light irradiation

Abstract

Cd1−xZnxS-sensitized K2Ti4O9 composite photocatalysts (hereafter designated as Cd1−xZnxS/K2Ti4O9) were prepared by a facile deposition–precipitation method. The samples were characterized by X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), ultraviolet–visible diffuse reflectance spectra (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). The photocatalytic activities for degradation of Rhodamine B (RhB) were investigated under visible light irradiation. The Cd0.8Zn0.2S particles, which were scattered on the surface of K2Ti4O9, had a relatively uniform size distribution centered around approximately 50nm, and the absorption edge of K2Ti4O9 was shifted to the visible light region after the deposition of Cd0.8Zn0.2S. The Cd0.8Zn0.2S crystal was found to be hexagonal and the K2Ti4O9 crystal monoclinic in the composite photocatalysts. Cd0.8Zn0.2S/K2Ti4O9 showed lower PL peak intensity than K2Ti4O9. The composite photocatalyst loaded with 30wt.% Cd0.8Zn0.2S exhibited the highest photo-catalytic activity, and was able to degrade 95% of RhB in 180min. The photocatalytic reaction parameters, such as initial RhB concentration, photocatalyst dosage and initial solution pH were studied. The mechanism of separation of the photo-generated electrons and holes in the Cd0.8Zn0.2S/K2Ti4O9 composite was also discussed.