Preparation of layered graphene and tungsten oxide hybrids for enhanced performance supercapacitors.

Tungsten oxide (WO3), which was originally poor in capacitive performance, is made into an excellent electrode material for supercapacitors by dispersing it on graphene (Gr). The obtained Gr-WO3 hybrids are characterized by X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy and scanning electron microscopy techniques, and evaluated as electrode materials for high-performance supercapacitors by cyclic voltammetry, galvanostatic charge-discharge curves and electrochemical impedance spectroscopy. A great improvement in specific capacitance is achieved with the present hybrids, from 255 F g-1 for WO3 nanoparticles to 580 F g-1 for Gr-WO3 hybrids (scanned at 1 A g-1 in 2 M KOH over a potential window of 0 to 0.45 V). The Gr-WO3 hybrid exhibits an excellent high rate capability and good cycling stability with more than 92% capacitance retention over 1000 cycles at a current density of 5 A g-1. The enhancement in supercapacitor performance of Gr-WO3 is not only attributed to its unique nanostructure with large specific surface area, but also its excellent electro-conductivity, which facilitates efficient charge transport and promotes electrolyte diffusion. As a whole, this work indicates that Gr-WO3 hybrids are a promising electrode material for high-performance supercapacitors.