The Supercapacitor Characteristics of Nano-Leaf Structured Iridium Oxide

• Main Authors: Cheng-Hsien Lin, 林政賢
• Other Authors: Ying-Sheng Huang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/40231968522564072954

碩士 === 國立臺灣科技大學 === 光電工程研究所 === 100 === In this thesis, high surface area IrOx nano-leaves (IrOxNL) with mesoporous structure were deposited on stainless steel (SS) and titanium (Ti) substrates by reactive radio frequency magnetron sputtering (RFMS). The optimal RFMS fabrication conditions of IrOxNL/SS and IrOxNL/Ti electrodes for pseudocapacitors have been determined to be: RF power of 30W, growth temperature of 100℃, growth time of 90 or 120 minutes and working pressure of 2.3 10-1 mbar. The surface morphology, structural and chemical compositions properties of the samples were characterized using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman scattering and X-ray photoelectron spectroscopy (XPS). The electrochemical characteristics were investigated by cyclic voltammetry (CV), electrochemical impedance spectrum (EIS) and galvanostatic charge-discharge measurements. The FESEM images of the as-deposited IrOxNL showed leaf-like morphology of iridium oxide. The XRD patterns indicated the as-deposited IrOxNL is amorphous. In Raman spectrum of IrOxNL, an additional weaker feature at ~360 cm-1 showed the as-deposited sample is non-stoichiometric. In addition, the redshifts and broadening of Raman scattering signals, compared with IrO2 single crystal, indicated the nanosized structural effects in IrOxNL. The XPS showed the surface of the as-deposited IrOxNL is composed of a mixture of iridium metal, iridium dioxide and iridium hydroxide. In the CV measurement, the rectangular I-V diagrams showed the reversible and capacitive characteristics of the as-deposited IrOxNL/SS and IrOxNL/Ti electrodes. The internal resistance of the electrodes was measured by EIS to be about 7 ohm. The charge-discharge curve exhibits a tiny IR drop, indicating a small DC resistance. The specific capacitance was then calculated from the discharged region of the charge-discharge curve. With long-term sweep cycles, we observed the extended cycle life property of IrOxNL/SS electrode with the specific capacitance maintained at about 230 F/g after 1000th cycle.