Effects of Carbon Nanotubes Acid Treated or Annealed and Manganese Nitrate Thermally Decomposed on Capacitive Characteristics of Electrochemical Capacitors

Abstract

Carbon nanotubes (CNTs) directly grown on aluminum foil or nanoporous alumina templates by chemical vapor deposition are treated with acid for different times or annealed at different temperatures. Then, the CNTs are immersed into a manganese nitrate aqueous solution and then manganese oxides are formed by thermally decomposing the manganese nitrate at different temperatures. The longer the time that the CNTs are treated with the acid, the slower the decreasing rate of the specific capacitance. Also, the higher the annealing temperature of the CNTs, the slower the decreasing rate of the specific capacitance. Furthermore, the electrochemical stability for thermally decomposing manganese nitrate at 400°C is better than that at 200 or 300°C and the operational stability with nanoporous alumina templates as a substrate is better than that with Al foil as a substrate.