Hydrothermal synthesis of magnetic graphene-BiFeO₃ hybrids and their photocatalytic properties

The graphene-bismuth ferrite (Graphene-BiFeO₃) hybrids with different graphene contents were synthesized by a hydrothermal method. Their structure was characterized by XRD, SEM and FTIR. Their light reflection and absorption were investigated by UV-visible diffuse reflectance spectroscopy and photoluminescence spectroscopy, respectively. Their photocatalytic properties were evaluated by degrading methylene blue (MB) and rhodamine B (RhB) dyes under irradiation with tungsten light. Results showed that the hybrids had a sphere-like morphology, within which the graphene was uniformly dispersed between the BiFeO₃ spheres. The hybrids had lower band gaps and higher absorption intensities in the visible light region (400-800 nm) than pure BiFeO₃, and achieved much higher degradation rates for both MB and RhB. The hybrid with a graphene content of 3.0 wt% exhibited the best photocatalytic performance, and its degradation rate constants for MB and RhB reached to 0.083 and 0.10, respectively, which are about 10 times higher than pure BiFeO₃. The introduction of the graphene effectively inhibited the recombination rate of the excited electrons and the holes in BiFeO₃. Their magnetism made them easy to recover from the dye solutions and their photocatalytic activities remained unchanged after recycling 5 times.