Characterization of sol-gel-derived cobalt oxide xerogels as electrochemical capacitors

• Published in: Journal of the Electrochemical Society 1998-12, Vol.145 (12), p.4097-4103
• Main Authors: CHUAN LIN, RITTER, J. A, POPOV, B. N
• Format: Article
• Language: English
• Subjects: Applied sciences; Capacitors. Resistors. Filters; Electrical engineering. Electrical power engineering; Exact sciences and technology; Various equipment and components
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.1838920

Very fine cobalt oxide xerogel powders were prepared using a unique solution chemistry associated with the sol-gel process. The effect of thermal treatment was found to have significant effects on the surface area, pore volume, crystallinity, particle structure and electrochemical properties of these xerogels. The xerogel remained amorphous as Co(OH)2 up to 160 C and exhibited maxima in surface area and pore volume at this temperature. Over 200 C, the surface area and pore volume decreased sharply, because the amorphous Co(OH)2 decomposed to form CoO which was subsequently oxidised to form crystalline Co3O4. The changes in surface area, pore volume, crystallinity and particle structure all had significant but coupled effects on the electrochemical properties of the xerogels. A maximum capacitance of 291 F/g was obtained for an electrode prepared with the CoOx xerogel calcined at 150 C, which was consistent with the maxima exhibited in both the surface area and pore volume; this capacitance was attributed solely to a surface redox mechanism. The cycle life of this electrode was also very stable for many thousands of cycles. 31 refs.