Preparation of graphene/Co3O4 composites by hydrothermal method and their electrochemical properties

In this study, graphene/Co3O4 composites are prepared through a simple process under mild hydrothermal conditions. Sodium carbonate (Na2CO3) can produce many OH- and CO32- ions after dissolution and hydrolysis in a water-isopropanol system, thereby making it applicable as both depositing agent and reducing agent in the synthesis of graphene/Co-2(OH)(2)CO3 composites. Remarkably, the galvanosta charge-discharge test shows that the specific capacitance value of the as-obtained composites reaches a high value of 443 F g(-1) at a high current density of 5 A g(-1), which is significantly improved in relation to Co3O4, and the capacitance retains 54% of capacitance at 60 A g(-1). The fact that the specific capacitance remains 97.1% after 1000 continuous charge-discharge cycles at 10 A g(-1) indicates that the as-prepared material has an excellent cycle life. The effect of the feeding ratios between Co3O4 and graphite oxide on the electrochemical performance has also been studied. (c) 2013 Elsevier Ltd. All rights reserved.