| Summary: | 博士 === 大同大學 === 材料工程學系(所) === 101 === Abstract
The specific capacitance of MnO2 thin film decreases with increasing film thickness due to the poor conductivity of MnO2 (10-5-10-6 S cm-1) and limit the charge/discharge rate for high-power applications .
Due to their excellent electrical conductivity and high specific surface area, Nanocomposite of manganese oxides/Au thin films were electrodeposited on ITO glass substrate by the potentiostatic method in KMnO4/AuCl3 aqueous solution. The thickness of the thin films was about 50~100nm composed of manganese oxide nanoparticles. MnOOH formed as the primary phase under electrodeposition without Au addition. The films exhibit the mixture of amorphous MnO2‧nH2O and MnOOH phases under electrodeposition with Au addition. The electrodes with 0.4% Au showed excellent capacitive behavior in the 0.1 M KNO3 electrolyte, with highest specific capacitance of 305F/g at a scan rate of 20mVs-1. The nanocomposite films became looser with lots of small crevices when Au was added from the SEM surface morphology observation. This gives smaller diffusion impedance and larger capacitance through the interconnected pores for proton diffusion. The electrode for nano-supercapacitors with silver/manganese oxides thin film were obtained by electrochemical deposition method. These thin films were potentiostaticly deposited (-0.7V v.s. open circuit) on ITO substrate with potassium permanganate and silver acetate solution for 200s. The thickness of the thin films was in the range of 100~300nm and composed of MnOx nanoparticles. The silver acted as a reduction agent and resulted in the valence change for Mn from +4 to 3+. Such a nanostructure of the thin film with MnOx nanoparticles and Ag2O results in much higher capacitance. It was suggested that the addition of silver oxide would promote the pseudo-capacitance by increasing the impedance of the thin films.
carbon nanotubes are now intensively used with MnO2 to make nanocomposites. In this study, multi-walled carbon nanotubes (MWCNTs) were used to make nanoconposites to improve the conductivity of manganese oxides films by spray coating technology. As a result, Mn(OH)2 did not only cover on the surface of MWCNTs uniformly but also embedded into MWCNTs.
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