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

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.