Reduced graphene oxide/titanium dioxide composites for supercapacitor electrodes: shape and coupling effects

Abstract

TiO₂ nanobelts (NBs) and nanoparticles (NPs) have been coupled with the chemically reduced graphene oxide (rGO) to form nanocomposites which are used as supercapacitor electrodes. The specific capacitance of rGO–TiO₂ composites is higher than that of monolithic rGO, TiO₂ NPs or NBs. The optimal electrochemical performance is achieved with the rGO–TiO₂ composites at a rGO : TiO₂ mass ratio of 7 : 3. In addition, the rGO–TiO₂ NBs exhibit better performance than the rGO–TiO₂ NPs in terms of specific capacitance, rate capability, energy density and power density. The specific capacitances of rGO–TiO₂ NBs and rGO–TiO₂ NPs with a mass ratio of 7 : 3 are 225 F g⁻¹ and 62.8 F g⁻¹ at a discharge current density of 0.125 A g⁻¹, respectively. The better performance of the rGO–TiO₂ NBs is attributed to the nanobelt's unique shape, better charge transport property and larger area of contact with the rGO nanosheet.