Preparation of reduced graphene oxide/cobalt oxide composites and their enhanced capacitive behaviors by homogeneous incorporation of reduced graphene oxide sheets in cobalt oxide matrix

Incorporation of reduced graphene oxide (rGO) in Co3O4 matrix is systematically investigated through a chemical route for supercapacitors. The alpha-Co(OH)(2) supported by graphene oxide is first fabricated by a chemical precipitation approach. Thermal decompositions of these precursors at the given temperature (150 degrees C) lead to rGO/Co3O4 composites. Measurement results show that the morphology and electrochemical activity of the rGO/Co3O4 composites are influenced significantly by the mass ratios of rGO to Co3O4. When used as electrode materials in supercapacitors, the composite with mass ratio of 0.22:1 (rGO:Co3O4) achieves the specific capacitance as high as 291 Fg(-1) at 1 A g(-1) in the potential range of -0.4 to 0.55 V, as compared with each individual counterpart (56 and 161 Fg(-1) for rGO and Co3O4, respectively). In addition, the excellent rate capability and well cycling ability are observed in the composite electrodes. The enhanced electrochemical performance is indicative of a positive synergistic effect between rGO and Co3O4. These results suggest the importance and great potential of graphene based composites in the development of high-performance energy-storage systems. (C) 2011 Elsevier B.V. All rights reserved.