High Photocatalytic Activity of Magnetically Separable Manganese Ferrite–Graphene Heteroarchitectures

A simple and straightforward strategy was developed to fabricate magnetically separable MnFe 2 O 4 –graphene photocatalysts with differing graphene content. It was found that graphene sheets were fully exfoliated and decorated with MnFe 2 O 4 nanocrystals having an average diameter of 5.65 nm and a narrow particle size distribution. It is very interesting that, although MnFe 2 O 4 alone is photocatalytically inactive under visible light irradiation, the combination of MnFe 2 O 4 nanoparticles with graphene sheets leads to high photocatalytic activity for the degradation of methylene blue under visible light irradiation. The strong magnetic property of MnFe 2 O 4 nanoparticles can be used for magnetic separation in a suspension system, and therefore it does not require additional magnetic components as is the usual case. Consequently, the MnFe 2 O 4 –graphene system becomes a dual function photocatalyst. The significant enhancement in photoactivity under visible light irradiation can be ascribed to the reduction of graphene oxide (GO), because the photogenerated electrons of MnFe 2 O 4 can transfer easily from the conduction band to the reduced GO, effectively preventing a direct recombination of electrons and holes. Hydroxyl radicals play the role of main oxidant in the MnFe 2 O 4 –graphene system, and the radicals’ oxidation reaction is obviously dominant.