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

Abstract

• Microsphere rGO/MnO 2 composites with varying reaction temperatures were synthesized via a simple route in a water-reflux condenser system. • RX-GMN@80 composite symmetric cell exhibits a prominent specific capacitance of 144 F g −1 at 1 mA current. • The RX-GMN@80 composite symmetric supercapacitor exhibits a high specific energy density of 28.7 Wh Kg −1 at a power density of 404 W Kg −1 . • Excellent cycling stability with 98.7% after 5000 cycles was observed. In the present work, microsphere MnO 2 /rGO (RX-GMN@X) composites were prepared for supercapacitor electrodes through a simple route in a water-reflux condenser system at three different temperatures (60, 80, and 100 °C). The composition and structure of MnO 2 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 microscopy (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 Na 2 SO 4 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.