Preparation and capacitive properties of cobalt-nickel oxides/carbon nanotube composites

In this paper, nickel-cobalt oxides/carbon nanotube (CNT) composites were prepared by adding and thermally decomposing nickel and cobalt nitrates directly onto the surface of carbon nanotube/graphite electrode to form nickel and cobalt oxides. Carbon nanotubes used in this paper were grown directly on graphite substrate by chemical vapor deposition technique. The capacitive behavior of nickel-cobalt oxides/CNT electrode was investigated by cyclic voltammetry and galvanostatic charge-discharge method in 1 M KOH aqueous solutions. The results show that nickel-cobalt oxides/CNT composite electrode has excellent charge-discharge cycle stability (0.2% and 3.6% losses of the specific capacitance are found at the 1000th and 2000th charge-discharge cycles, respectively) and good charge-discharge properties at high current density. Additionally, the effect of Ni/Co molar ratio on specific capacitance of the composite electrode was investigated and the highest specific capacitance (569 F g(-1) at 10 mA cm(-1)) is obtained at Ni/Co molar ratio = 1:1. (c) 2006 Elsevier Ltd. All rights reserved.