Activation Mechanism Study of Dandelion-Like Co9S8 Nanotubes in Supercapacitors

Dandelion-like Co9S8 nanotubes have been fabricated by a mild two-step hydrothermal method and applied as electrode materials in supercapcitors. An unusual activation process of the as-prepared electrode is revealed through electrochemical characterizations and morphology transmutations. During the initial charge-discharge process, CO9 S8OH nanosheets are formed and accumulated on the Co9S8 nanotubes, which largely enhance the contact surface area between electrode and electrolyte and result in an improvement of specific capacitance. After activation of electrodes, the specific capacitance can be dramatically increased by 9.2% from 261.3 F g(-1) to 285.3 F g(-1) at current density of 2 A g(-1), and that is favorable to the performance of supercapacitors. The stability of the as-prepared electrodes are also studied, high coulombic efficiency of 97% and cycle life of 90.4% are also observed after 1000 cycles. All the characters performed by the as-prepared CO9 S-8 nanotubes exhibit its potential as an electrode material for supercapacitors. (C) 2014 The Electrochemical Society.