High performance electrochemical supercapacitors based on electrodeposited RuO₂on graphene sheet electrodes

Ruthenium oxide (RuO₂) electrode films with nanoscale morphologies were prepared on flexible Cu and Cu/graphene papers by using a cost-effective electrodeposition technique. Uniform spherical RuO₂ grains formed on the graphene/Cu substrate while agglomerated RuO₂ grains were observed on the Cu substrate. The RuO₂/graphene/Cu electrode exhibited a high specific capacitance of ∼930 F/g at a 5 mV/s scan rate, a comparably good electrochemical stability about 55% after 500 charge-discharge cycles, and a good rate capability. The specific capacitance of the RuO₂/graphene/Cu electrode was of approximately three times more than that of the RuO₂/Cu electrode (∼303 F/g), and the same ratio was maintained even for a 100 mV/s scan rate. The improved specific capacity of the RuO₂/graphene/Cu was a result of the synergetic effect of the graphene and RuO₂, which resulted in a large effective surface area and leads to an increase in the Li⁺² ions and that are adsorbed and charge transport with greater ease.