▎ 摘　　要

Magnetic Bi25FeO40-graphene visible-light photocatalysts were prepared by a one-step alkaline hydrothermal method and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, Raman spectroscopy, X-ray photoelectron spectra (XPS) and magnetic hysteresis loop measurements. XRD characterization indicated that under identical hydrothermal conditions, perovskite type bismuth ferrite (BiFeO3) was obtained without graphene addition, while the presence of graphene led to the formation of sillenite type bismuth ferrite (Bi25FeO40). In contrast to BiFeO3, the Bi25FeO40-graphene composite was superparamagnetic, and could be readily recovered in an external magnetic field. Additionally, Bi25FeO40-graphene photocatalyst exhibited higher catalytic activity for the degradation of methylene blue (MB) under visible-light irradiation than BiFeO3 and Bi25FeO40. This is due to enhanced MB adsorption and effective suppression of electron-hole recombination via preferential electron transfer from Bi25FeO40 to graphene. Moreover, increasing graphene content enhanced the catalytic activity of the composite catalyst. Accordingly, the photocatalytic MB degradation over Bi25FeO40-(20) graphene followed the Langmuir-Hinshelwood model, indicative of an adsorption controlled reaction mechanism.