Solar-assisting pyrolytically reclaimed carbon fiber and their hybrids of MnO2/RCF for supercapacitor electrodes

By using solar energy as the power source, aligned and clean reclaimed carbon fibers (RCFs) were successfully recovered from carbon fiber-reinforced polymer (CFRP). Furthermore, α-MnO2 nanowires were grown on the RCF surface through a one-step hydrothermal process, and thus MnO2/RCF composite was successfully prepared. Both the RCF and MnO2/RCF can be directly utilized as supercapacitor electrode, and the electrochemical performance of the electrode materials were evaluated by utilizing cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a three-electrode cell. RCF electrode exhibited a favorable performance with a prolonged potential window (−1.6-0 V) in a 2 mol L−1 of aqueous KOH solution, while the MnO2/RCF electrode prepared at 150 °C showed a superior electrochemical performance in a 1 mol L−1 of aqueous Na2SO4 solution: a specific capacitance of 228.8 F g−1 at 1 A g−1 and high cycling stability (about 91.2% capacitance retention after 3000 cycles). A MnO2/RCF-based asymmetric supercapacitor was assembled, which exhibited excellent performances with a voltage window of 2.0 V, a high energy density of 22.9 Wh kg−1 and a remarkable cycling stability (89% capacitance retained after 1000 cycles at 2.25 A g−1).

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