External Magnetic Field-Enhanced Supercapacitor Performance of Cobalt Oxide/Magnetic Graphene Composites

The effect of an external magnetic field on the supercapacitor performance of cobalt oxide/magnetic graphene composites has been investigated. The composites were prepared via the hydrothermal reaction of cobalt nitrate with iron oxideincorporated magnetic graphene. Cobalt oxide nanoparticles were deposited on the graphene sheets and contributed to enhancing the electrochemical capacitance, since the cobalt oxide could work as pseudocapacitance material different from the graphene sheet with the electric double-layer capacitance effect. Further enhancement was observed upon applying the external magnetic field, which was increased via a home-made electric circuit. The specific capacitances of the composite materials under the external magnetic field of 1191 Gauss were found to be a maximum of 11 times higher than those without the magnetic field. It was also suggested that the increase in specific capacitance under the magnetic field follows the power law of the magnetic field due to a magnetohydrodynamic effect. These results demonstrate the importance of the external magnetic field to develop new technologies on energy-related applications of magnetic materials.