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.