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.

Automated summary

A facile solvothermal synthesis method was reported for producing novel octahedral CoFe2O4-RGO hybrid and pure CoFe2O4 as heterogeneous photo-Fenton catalysts for organic dye degradation. The octahedral CoFe2O4-RGO hybrids exhibited higher saturation magnetization values and excellent catalytic activity for H2O2 activation at nearly neutral pH, while also showing enhanced removal efficiency for cationic dyes under visible light irradiation. The graphene/CoFe2O4 heterojunction in the hybrids aided in electron-hole separation and contributed to the improved photo-Fenton activity.