Abstract
Two MnO2 samples (MO-1 with thorn spheres and MO-2 with long nanowires) were synthesized by adding urea into KMnO4–H2SO4 reaction system at various hydrothermal temperatures. Urea could decrease the reaction temperature, and its hydrolysis could influence the morphology of MnO2. The as-prepared samples were analyzed by XRD and SEM. Their capacitive properties were investigated by electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge/discharge test. The initial specific capacitance values of AC//MO-1 and AC//MO-2 hybrid capacitors were 24.99 and 27.58 F g−1 in 1 M Li2SO4 electrolyte, respectively. After 1000 cycles, the capacitance retention was 91.40% for AC//MO-1 and 96.93% for AC//MO-2. Therefore, AC//MO-2 exhibited better capacitive properties than AC//MO-1.
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