Solvothermal synthesis of octahedral and magnetic CoFe2O4-reduced graphene oxide hybrids and their photo-Fenton-like behavior under visible-light irradiation

We report a facile solvothermal synthesis of novel octahedral CoFe2O4-reduced graphene oxide (RGO) hybrid and pure CoFe2O4 that were used as heterogeneous photo-Fenton catalysts for the degradation of organic dyes in water. We investigated the structures, morphologies and catalytic activity of both the CoFe2O4 nanoparticles and CoFe2O4-RGO hybrids. The morphology of CoFe2O4 nanoparticles displays size-dependent shapes changing from granular (or sheet) to octahedral shapes with the introduction of RGO. Compared with bare CoFe2O4, the octahedral CoFe2O4-RGO hybrids serve as novel bifunctional materials displaying higher saturation magnetization values and excellent heterogeneous activation of H2O2 at nearly neutral pH. The high saturation magnetization (41.98 emu g(-1)) of CoFe2O4-RGO hybrids aids their separation from the reaction mixture. In addition, the remarkable enhancement in the photo-Fenton activity of the CoFe2O4-RGO hybrids under visible light irradiation was attributed to the graphene/CoFe2O4 heterojunction, which aided the separation of excited electrons and holes. Furthermore, the CoFe2O4-RGO hybrids exhibited better removal efficiency for cationic methylene blue (MB) dye than for anionic methyl orange (MO) dye. Meanwhile, the CoFe2O4-RGO hybrids displayed acceptable photocatalytic stability, and we proposed an activation mechanism of H2O2 by the octahedral CoFe2O4-RGO hybrids.