Construction of ZnFe2O4/rGO composites as selective magnetically recyclable photocatalysts under visible light irradiation.

This paper reports on highly active ZnFe2O4/reduced graphene oxide (ZnFe2O4/rGO) nanocomposites synthesized by a modified sol-gel method. The as-prepared samples have been characterized by XRD, TEM, XPS and other detection methods, which demonstrate that ZnFe2O4 nanoparticles (NPs) with a diameter of 15 ∼ 50 nm were densely grown on the rGO substrates. The photocatalytic activities of ZnFe2O4/rGO catalysts were evaluated by the degradation of Methylene blue (MB) under visible light. The results showed that the ZnFe2O4/rGO catalysts had high photocatalytic activity, and the degradation efficiency of MB was almost 100% within 180 min. Moreover, the ZnFe2O4/rGO catalysts also had a great removal effect on Rhodamine B (RhB) and Methyl orange (MO). Mechanistic studies revealed that the rGO acted as a stabilizer to prevent ZnFe2O4 from aggregation and improved the separation of photo-generated electrons. The high efficiency for dye degradation was attributed to the generation of hydroxyl radicals (·OH) via the photochemical decomposition of H2O2 on ZnFe2O4/rGO catalysts, which was responsible for the oxidation of the dyes. Of note, the ZnFe2O4/rGO catalyst maintained an efficiency of over 90% after five cycles. The XRD, XPS and VSM characterization revealed that the ZnFe2O4/rGO catalysts had a stable crystal structure and can be easily separated.