Supercapacitors based on high-surface-area graphene

Exfoliated graphite oxide was prepared by an improved Hummers method and was then reduced to graphene with hydrazine in the presence of ammonium hydroxide. N-2 adsorption-desorption measurement showed that graphene so obtained had a specific surface area as high as 818 m(2)/g. Galvanostatic charge/discharge curves demonstrated that the as-prepared graphene exhibited a specific capacitance of 186.9 F/g at a current density of 0.1 A/g and that about 96% of the specific capacitance was retained after 2000 cycles at a current density of 5 A/g.