Photocatalytic Degradation of Dyes by ZnIn₂S₄ Microspheres under Visible Light Irradiation

Abstract

ZnIn2S4 microspheres were successfully synthesized by a hydrothermal method. A series of synthesis temperatures from 80 to 200 °C was investigated. The samples were characterized by X-ray diffraction, UV−vis spectroscopy, nitrogen sorption analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy (SEM). The results indicated that the crystalloid structure and optical property of temperature series products were almost the same. The specific surface area (SBET) of ZnIn2S4 products declined with increasing synthesis temperature. The 80 °C sample had the largest SBET (85.53 m2 g−1). SEM images demonstrated that the morphology of ZnIn2S4 was marigold-like microspheres, and the 80 °C sample had a well-proportioned morphology. Several dyes (methyl orange, congo red, and rhodamine B) were applied in the ZnIn2S4 photocatalytic reactivity investigation. It showed efficient visible light photocatalytic degradation of dyes. A liquid chromatogram−mass spectrometer was used for identification of dyes and their degradation products. A large number of ·OH radicals, investigated by the method of photoluminescence with terephthalic acid, were generated in the photocatalyst system. The results indicated that the ·OH radicals played an important role in the superior visible photocatalytic activity of the ZnIn2S4 system. The mechanism related to the photocatalytic degradation was proposed and discussed.