Preparation and Electrochemical Performance of Thin Layer Crystal α-MnO2/AC Composite Electrode Materials

The composite electrode materials of alpha-MnO2/activated carbon (alpha-MnO2/AC) were prepared by in-situ hydrothermal deposition using ammonium persulfate as oxidants, manganese sulfate as precursors, ammonium sulfate as templates and self-made activated carbon as supports. X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption at 77 K were used to investigate the crystal structure, morphology, specific surface area and porosity of the composites, respectively. Their electrochemical properties were evaluated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The results showed that crystalline alpha-MnO2 was well deposited on the AC to produce thin layer crystal alpha-MnO2/AC composite material at the optimal MnSO4 concentration of 0.075 mol.L-1 the synthetic process. The specific capacitance of the composite could be as high as 374.5 F.g(-1), 48.2% higher than that of pure AC electrode. The alpha-MnO2/AC composite electrode had high stability and the capacity retention was of 95% after a 1000-cycle charge-discharge.