Thesis (M.Sc.)--Chulalongkorn University, 2008

In this work, the preparation of metal oxide (FeO and NiO) and titanium-based multi-walled nanotube (MWNTs) composites for capacitor electrodes was reported. The composite materials were synthesized via a chemical reduction method using metal salts and functionalized MWNTs. Structural and morphological characterizations of these composites were carried out via x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesized composites were dispersed in an aqueous solvent via sonication, and then the composite solutions were then electrostatically sprayed onto the Pt/Si substrates which were heated to 1500C. Cyclic voltammetry, impedance spectroscopy and galvanostatic technique were employed to characterize the electrochemical performances of the composite thin films. Electrochemical characterization shows that there is an almost linear dependence of structure-specific capacitance on the amount of metal oxides on the MWNTs surface due to the surface’s pseudo-capacitive nature. From the results, the composite electrode obtained from NiO incorporated on TiO2/MWNTs provides a markedly enhanced specific capacitance of 180.40 F/g in 1 M H2SO4. Such an enhanced capacitance, as well as the cost-effectiveness of the NiO on TiO2/MWNTs composite, shows the advantages to the use of this composite as an effective alternative material for electrochemical capacitors.