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

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