Monodisperse carbon microspheres derived from potato starch for asymmetric supercapacitors

Uniform and monodisperse carbon microspheres (MCMSs) are synthesized via a catalyst-free and hydrothermal process by following a high temperature carbonization, in which potato starch is used as raw material. The morphology and microstructure of the as-obtained samples are characterized using SEM, TEM, XRD, Raman, FTIR and BET. TEM image shows that the products consist of carbon microspheres with a mean diameter of about 250 nm. BET specific surface area of MCMSs is up to 456 m2·g−1. Furthermore, the supercapacitive performances of the MCMSs are investigated by cyclic voltammogram (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS). The experimental results indicate that the MCMSs exhibits not only high specific capacitance of 245 F·g−1 and good rate capability (the specific capacitance at 10 A·g−1 is 61% of that at 1 A·g−1), but also excellent cycle stability (no obvious capacitance decay after 4,000 cycles at 3 A·g−1). An asymmetric electrochemical capacitor is assembled by using the obtained MCMSs as negative electrode and reduced graphene oxide (RGO) as positive electrode. The as-assembled MCMSs//RGO capacitor can cycle reversibly in a voltage of 0–1.5 V and give a high energy density of 21.5 Wh·kg−1 at a power density of 759 W·kg−1.

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