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

Abstract

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.