Preparation of mesoporous nanocrystalline Co3O4 and its applicability of porosity to the formation of electrochemical capacitance

In this paper we describe a new synthesis strategy for preparing loose-packed porous materials with the particle diameter down scaled to nanometer size. Mesoporous nanocrystalline Co3O4 was prepared using this method, and an attempt was made to apply it as an active electrode material for electrochemical capacitors. The composition and microstructure of the resulting nanocrystalline material were investigated by X-ray diffraction spectroscopy and high-resolution transit electron microscopy (HRTEM). Based on the value of d(111) from HRTEM, the molecular formula of Co3O4 was obtained by comparing it with those of CoO and Co2O3. Static adsorption and desorption isotherm (SADI) analysis show that porous nanocrystalline Co3O4 prepared by this method has a high Brunauer-Emmett-Teller (N-2) surface area (212 m(2)/g) with mesopore distributions. The formation mechanism of mesoporous nanocrystalline Co3O4 was proposed based on Fourier transform infrared spectroscopy and SADI analysis. Electrochemical studies revealed that the electrode prepared with this kind of material exhibits a high specific capacitance of 401 F/g. The charge-storage mechanism of the measured capacitance was investigated. In addition, the electrochemical processes, such as ion transfer and electrical conduction, were investigated with electrochemical impedance spectroscopy. The correlation between the microstructure and the energy density as well as the power density is discussed. (c) 2005 The Electrochemical Society.