Facile and green synthesis of Co3O4 nanoplates/graphene nanosheets composite for supercapacitor

A series of Co3O4 nanoplates/graphene nanosheets (GNS) composites are fabricated using a facile and green method by hydrothermal treatment and subsequent calcinations in air. The Co3O4 nanoplates with a length of 0.5-1 mu m and width of 100-300 nm are homogeneously distributed on the surface of graphene nanosheets which are reduced under mild hydrothermal treatment as investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Electrochemical properties are tested by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The Co3O4 nanoplates/7.0 % GNS composite shows a maximum specific capacitance of 667.9 F g(-1) at 1.25 A g(-1) and 412.5 F g(-1) at 5 A g(-1) in 2 M KOH aqueous solution. The composite exhibits excellent cycling stability with 18.7 % of specific capacitance increased after 1,000 cycles.