LAUSR

Novel highly visible-light active 1.0rGO–ZnBi 2 O 4 –Bi 2 S 3 heterostructure photocatalysts with various weight percentages of Bi 2 S 3 were successfully synthesized. First, the 1.0rGO–ZnBi 2 O 4 catalyst was synthesized by a simple two-step oxidation–reduction and co-precipitation methods, followed by heating at 450 °C. Then, 1.0rGO–ZnBi 2 O 4 was hydrothermally treated with Bi 3+ , and thiourea in ethylene glycol to obtain the 1.0rGO–ZnBi 2 O 4 –Bi 2 S 3 heterostructure photocatalyst. The obtained 1.0rGO–ZnBi 2 O 4 –Bi 2 S 3 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–ZnBi 2 O 4 –2.0Bi 2 S 3 heterostructure photocatalyst is due to the homogeneous distribution of ZnBi 2 O 4 –2.0Bi 2 S 3 over rGO as well as to the efficient electron-transfer from Bi 2 S 3 to ZnBi 2 O 4 and finally to rGO. More than 97% of Indigo carmine of 50 mg/L was degraded by 1.0rGO–ZnBi 2 O 4 –2.0Bi 2 S 3 in 75 min of visible light irradiation. The reusability of the 1.0rGO–ZnBi 2 O 4 –2.0Bi 2 S 3 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–ZnBi 2 O 4 –2.0Bi 2 S 3 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.