Low-temperature and template-free fabrication of cobalt oxide acicular nanotube arrays and their applications in supercapacitors

Layered cobalt carbonate hydroxide (LCCH) acicular nanorod arrays (ANRAs) grown on a graphite substrate are converted to Co3O4 acicular nanotube arrays (ANTAs) via the anion-exchange reaction and Kirkendall effect at low temperature. The Co3O4 ANTAs exhibit an area capacitance of 369 mF cm(-2) and a specific capacitance of 979 F g(-1) at 2.5 mA cm(-2), which are much higher than those of the Co3O4 ANRAs prepared by calcining the LCCH ANRAs at 350 degrees C (64.5 mF cm(-2) and 191 F g(-1)).