Electrochemical Capacitance from Carbon Nanotubes Decorated with Cobalt Oxide Nanoparticles in Alkali Electrolyte

摘要

Deposition of cobalt oxide nanoparticles on CNTs was performed to examine the influence of Co_3O_4 loading on the electrochemical capacitance of CNT electrodes. X-ray diffraction revealed that the Co_3O_4 belongs to spinel crystalline structure. Cyclic voltammetric study on the resulting electrodes showed that both of contributor of pseudocapacitance and double-layer capacitance increase significantly after the deposition of Co_3O_4. Constant current charge-discharge cycling also reflected the capacitance enhancement contributed from Co_3O_4 deposition, i.e., an increase of capacitance from 83.5 F/g to 185.5 F/g at a current density of 0.5 mA/cm~2. This result reflected that attached Co_3O_4 can be served as an electroactive site in facilitating an additional specific capacitance. Equivalent circuit analysis on impedance spectra indicated that both of electrical connection and charge transfer resistances accounted for the major proportion of the overall resistance and were found to slightly decrease after the attachment of Co_3O_4.