Porous CoO nanostructures grown on three-dimension graphene foams for supercapacitors electrodes

Three-dimensional graphene foams with good conductivity, light weight and chemical stability were produced by chemical vapor deposition. Then porous CoO nanowalls were deposited on graphene foam by a simple hydrothermal process and subsequent thermal treatment. This hybrid structures possessing large surface area in which the CoO nanowalls are separated by graphene foam with robust adhesion can directly serve as supercapacitor electrode including current collector without the need of any other binder materials and conductive agents. Electrochemical tests manifest a high specific capacitance of 231.87 F/g scaled to the mass of CoO (139.47 F/g for total mass of electrodes) at 1 A/g current, good rate capability and excellent cycling performance of >98% capacitance retention over 1000 cycles at 7 A/g current. The high conductivity, light weight and rational architectures, which provide fast electron pathway and the low diffusion resistance of ions, are responsible for the high performance of the electrodes.