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We have prepared Fe3O4/reduced graphene oxide (rGO) hybrid materials via a simple, cost-effective hydrothermal technique in ambient conditions by combining with growth of Fe3O4 NPs with the reduction of graphene oxide in a one-pot synthesis. This hybrid material has been used to fabricate the electrodes of an electrochemical double layer supercapacitor having a specific capacitance of 451 F g−1 at a scan rate of 5 mV s−1. The external magnetic fields have a huge impact on the electrochemical processes which enhance the supercapacitor performance of the magnetic samples. The as-synthesized Fe3O4/rGO hybrid possesses high surface area, and an external magnetic field (0.125 T) allows electrolyte ions to penetrate deeper into the orifices of the electrode surface—i.e. ions can reach extra electrode surface—and thus improves the capacitance. As a result, the hybrid electrode in the presence of such a magnetic field exhibits a specific capacitance (868.89 F g−1) which is 1.93 times higher than that without any magnetic field. In addition, the energy density and power density of the hybrid electrode in the presence of magnetic field are noticeably improved to 120.68 Wh kg−1 and 3.91 kW kg−1, respectively. These findings suggest a potential revolution to improve the capacitance of traditional supercapacitors significantly in the presence of external magnetic fields, without material replacement.

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Mixed solvent exfoliated transition metal oxide nanosheet/SWCNT composite based flexible supercapacitors demonstrate large specific capacitance and high energy density.

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