Electrochemical properties of spinel-type manganese oxide/porous carbon nanocomposite powders in 1 M KOH aqueous solution

Spinel-type manganese oxide/porous carbon (Mn₃O₄/C) nanocomposite powders have been simply prepared by a thermal decomposition of manganese gluconate dihydrate under an Ar gas flow at above 600 °C. The structure and texture of the Mn₃O₄/C nanocomposite powders are investigated by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) equipped scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), selected area-electron diffraction (SA-ED), thermogravimetric and differential thermal analysis (TG-DTA) and adsorption/desorption of N₂ gas at ?196 °C. The electrochemical properties of the nanocomposite powders in 1 M KOH aqueous solution are studied, focusing on the relationship between their structures and electrochemical capacitance.In the nanocomposite powders, Mn₃O₄ nano particles approximately 5 nm in size are dispersed in a porous carbon matrix. The nanocomposite powders prepared at 800 °C exhibit a high specific capacitance calculated from cyclic voltammogram of 350 and 600 F g^?1 at a sweep rate of 1 and 0.1 mV s^?1, respectively. The influence of the heating temperature on the structure and the electrochemical properties of nanocomposite powders is also discussed.