In-situ synthesis of expanded graphite embedded with CuO nanospheres coated with carbon for supercapacitors

Expanded graphite embedded with CuO nanospheres coated with carbon (EG/CuO@C) is in-situ prepared by self-combustion and hydrothermal treatment methods The component analysis of the composite is carried out using X-ray diffraction and its morphology and microstructure are characterized using field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM). The electrochemical performance is examined by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy in 6 M KOH solution as electrolyte. The experimental results revealed that the EG/CuO@C composite remained porous structure, which is beneficial for supercapacitance. The EG/CuO@C exhibits the high specific capacitance of 335 F g⁻¹ and the capacitance retention of 87% after 8000 cycles at the scan rate of 10 mV s⁻¹. Moreover, the EG/CuO@C composite remains high energy density of 14.03 Wh kg⁻¹ at the power density of 10.1 kW kg⁻¹.