Facile synthesis of pompon-like manganese dioxide decorated activated carbon composite for supercapacitor electrode

Coupling carbon materials and metal oxide is one of the most effective strategies for promoting the energy storage performance of supercapacitor electrode materials. This study prepared a novel pompon-like activated carbon/manganese dioxide nanosheet composite (AC-MnO2–1) via a facile and cost-efficient strategy starting with a reduction reaction at room temperature between potassium permanganate (KMnO4) and activated carbon (AC). The morphologies of nanocomposites and the mass loading of manganese dioxide (MnO2) on AC could be manipulated by altering the reaction time between the AC and KMnO4. The structure and morphology were measured using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of the electrode materials was evaluated via cyclic voltammetry (CV), galvanostatic charging-discharging (GCD), and electrochemical impedance spectroscopy (EIS) tests in 1 M Na2SO4 aqueous electrolytes. The as-prepared AC-MnO2–1 sample exhibited a specific capacitance of 177.4 F g−1 at a current density of 1 A g−1. Moreover, the capacitance retention rate of AC-MnO2–1 reached 99.72 % even at a high current density of 10 A g−1 after 10,000 cycles. Regarding practical applications, a symmetric supercapacitor (SSC) was assembled using this nanocomposite as the positive and negative electrode material. In addition, the aqueous SSC cell showed a specific capacitance of up to 80.3 F g−1 and an energy density of 18.0 W h kg−1 at a power density of 899.6 W kg−1 at a constant current density of 1 A g−1 with an expanded potential frame of 1.8 V. The result also provided a feasible method for the industrialization of the AC-MnO2 nanocomposite due to easy operation, time/energy efficiency and inexpensive reagents.