MWCNTS/Nickel Oxide Nanocomposite Supercapacitor Made from Two Electrode Coin Type Cells

Studies have shown that carbon nanotubes-metal oxide (CNT/MO) nanocomposite modified electrodes exhibited huge capacitive current in some electrolytes [1-6]. Therefore, it becomes imperative to establish the charge storage properties of these materials as a potential source for energy generation in acidic and neutral medium since most reported work has been conducted in an alkaline environment. In this work, supercapacitive property of synthesised nickel oxides (NiO) nanoparticles integrated with multi-walled carbon nanotubes (MWCNT) in an acidic medium using a two-electrode coin cell type supercapacitor was investigated. Successful formation of the MWCNT-NiO nanocomposite was confirmed with techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The supercapacitive behaviour of both the symmetry and the asymmetry MWCNT-NiO based supercapacitor in 1 M H₂SO₄ and 1 M Na₂SO₄ electrolytes was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic constant current charge-discharge (CD) techniques. There was a good correlation between the CV and the CD specific capacitance (SC) values for the asymmetry supercapacitor. Asymmetry supercapacitor (MWCNT-NiO|H₂SO₄|MWCNT) gave the highest SC value of 925.9 mFcm^-2 (53.9 F g^-1) and energy deliverable efficiency of 101.0±8.1%. High SC values which are higher than most of those reported in literature were obtained. The electrodes demonstrated high stabilities with no significant changes in SC values over 1000 cycles.

References:

1. A.S. Adekunle, K.I. Ozoemena, Electrochim. Acta 53 (2008) 5774.

2. A.S. Adekunle, K.I. Ozoemena, J. Solid State Electrochem. 12 (2008) 1325.

3. B.E. Conway, Electrochemical Super Capacitors, Kluwer Academic/Plenum Publishers, New York, 1999.

4. M. Winter, R.J. Brodd, Chem. Rev. 104 (2004) 4245.

5. Y.H. Lee, K.H. An, J.Y. Lee, S.C. Lim, Encycl. Nanosci. Nanotechnol. 1 (2004) 625.

6. E. Frackowiak, F. Beguin, Carbon 40 (2002) 1775.