Visible-Light Degradation of Organic Dye Based on a Heterostructure Photocatalyst

Abstract

Novel highly visible-light active 1.0rGO–ZnBi2O4–Bi2S3 heterostructure photocatalysts with various weight percentages of Bi2S3 were successfully synthesized. First, the 1.0rGO–ZnBi2O4 catalyst was synthesized by a simple two-step oxidation–reduction and co-precipitation methods, followed by heating at 450 °C. Then, 1.0rGO–ZnBi2O4 was hydrothermally treated with Bi3+, and thiourea in ethylene glycol to obtain the 1.0rGO–ZnBi2O4–Bi2S3 heterostructure photocatalyst. The obtained 1.0rGO–ZnBi2O4–Bi2S3 heterostructure photocatalysts were characterized by X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Photocatalytic studies were conducted using Indigo carmine and it was found that the heterostructure photocatalyst enabled an almost complete degradation of the pollutants. The enhanced catalytic activity of the 1.0rGO–ZnBi2O4–2.0Bi2S3 heterostructure photocatalyst is due to the homogeneous distribution of ZnBi2O4–2.0Bi2S3 over rGO as well as to the efficient electron-transfer from Bi2S3 to ZnBi2O4 and finally to rGO. More than 97% of Indigo carmine of 50 mg/L was degraded by 1.0rGO–ZnBi2O4–2.0Bi2S3 in 75 min of visible light irradiation. The reusability of the 1.0rGO–ZnBi2O4–2.0Bi2S3 was studied, and after four cycles, the Indigo carmine degradation efficiency decreased to 90%.The mechanism of the Indigo carmine degradation by the 1.0rGO–ZnBi2O4–2.0Bi2S3 catalysis likely consists of to two main processes: first, charge transfer prolongs the lifetime of the electron–hole pairs, and then the electron–hole pairs participate in the reactions that produce free radicals.