Microsphere rGO/MnO2 composites as electrode materials for high-performance symmetric supercapacitors synthesized by reflux reaction

In the present work, microsphere MnO2/rGO (RX-GMN@X) composites were prepared for supercapacitor elec-trodes through a simple route in a water-reflux condenser system at three different temperatures (60, 80, and 100 degrees C). The composition and structure of MnO2 and RX-GMN@X composites were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), energy dispersive X-ray analysis (EDAX), and X-ray photoelectron spectroscopy (XPS). The morphology of samples is analyzed by transmission electron mi-croscopy (TEM) and scanning electron microscopy (SEM). The surface area is measured by Brunauer-Emmett-Teller analysis (BET). The high surface area and abundant porosity of RX-GMN@80 enable more adsorption sites to shorten the ion diffusion pathway. Electrochemical studies investigated that RX-GMN@80 composite material exhibit excellent specific capacitance of 630 F g-1 in three electrodes configuration with 1 M Na2SO4 aqueous electrolyte. RX-GMN@80 composite symmetric supercapacitor displays a high specific capacitance of 144 F g-1 and possesses a maximum energy density of 28.7 Wh kg-1 at a charging current of 1 mA. Furthermore, the composite exhibits long cycle life and 98.7% efficiency maintained after 5000 cycle tests at a charging current of 3 mA.