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A nanoscale hydrous manganese oxide used as an electrode in a supercapacitor was deposited onto a titanium substrate from an aqueous manganese acetate solution using the hydrothermal electrochemical method. The effect of deposition temperature on the characteristics of the manganese oxides was investigated. The capacitive characteristics of the manganese oxides were measured in sulfate electrolytes with various cations using cyclic voltammetry. The capacitive performances of the manganese oxide electrodes depend on the deposition temperature as well as the cations of electrolytes. A maximum capacitance of 244 F g −1 was obtained in Na 2 SO 4 solution. The stability of manganese oxide was examined; after 1000 cycles, 80% of the initial capacitance remained.

For application in a supercapacitor as electrodes, nano-scaled manganese oxide films were deposited on titanium substrates in manganese acetate solution using the hydrothermal electrochemical process. The effects of synthesis temperature, pH, and the concentration of manganese acetate on the material characteristics and capacitive behavior of manganese oxide film were investigated. The complex tri- and divalent hydrous manganese oxides examined using X-ray photoelectron spectroscopy (XPS) and Raman scattering spectroscopy were obtained at 60 °C in 0.2 M neutral solution. A maximum specific capacitance (SC) of 244 F g-1 was measured using cyclic voltammetry (CV) at 25 °C in 0.1 M Na2SO4 within the range of 0–1 V. The nanometer scale surface morphology of the film was altered by varying the synthesis temperature, pH, and the concentration of the solution. In addition to the surface morphology, the extent of hydration in the manganese oxide film also affected the capacitive properties.

Nanometer-scale manganese oxide films were synthesized at various temperatures in the range of 60–150 °C using the hydrothermal electrochemical deposition method. Field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were used to verify that the deposits were tri- and divalent hydrous manganese oxides. The electrochemical performance of manganese oxide films was examined by cyclic voltammetry (CV) in the range of 0.0–1.0 V [versus saturated calomel electrode (SCE)] in 0.1 M Na2SO4 solution at 25 °C. The specific capacitance (SC) increased with decreasing synthesis temperature, with a maximum value of approximately 244 Fg-1 at 60 °C. Crystalline manganese oxide prepared at 150 °C improved stability of capacitive performance, which only decreased by 4% after 800 cycles. The SC depended not only on the surface morphology but also on the amount of hydration in the manganese oxide structure. The deposited manganese oxide has the chemical formula Mn3O4nH2O (n~1.2), as established using thermogravimetric and differential thermal analysis (TG/DTA).

To improve the performance of manganese oxides applying to electrochemical capacitor as electrodes, the hydrothermal electrochemical deposition method was used for preparing the manganese oxide films. The optimum synthesis conditions and each synthesis factor (such as solution concentration, synthesis temperature, deposition time and deposition voltage) contributing to the specific capacitance of synthesized manganese oxides were approached by using Taguchi experimental design method. The synthesis temperature and concentration of manganese acetate were the two main factors influencing the specific capacitance. The manganese oxide films deposited under the solution concentration of 0.2 mol L -1 , synthesis temperature of 100°C, deposition time of 60 s, and deposition voltage of 0.8 V showed the optimum specific capacitance of ca. 126.35 Fg -1 . Porous and needle-like morphology enhanced the specific capacitance of manganese oxide film but restricted the stability performance of charge/discharge. The crystalline Mn 3 O 4 and denser morphology revealed the good stable ability of capacitive performance after 600 cyclic-life test.