High Performance of N-Doped Graphene with Bubble-like Textures for Supercapacitors.

Nitrogen-doped graphene (NG) with wrinkled and bubble-like texture is fabricated by a thermal treatment. Especially, a novel sonication-assisted pretreatment with nitric acid is used to further oxidize graphene oxide and its binding with melamine molecules. There are many bubble-like nanoflakes with a dimension of about 10 nm appeared on the undulated graphene nanosheets. The bubble-like texture provides more active sites for effective ion transport and reversible capacitive behavior. The specific surface area of NG (5.03 at% N) can reach up to 438.7 m2 g-1 , and the NG electrode demonstrates high specific capacitance (481 F g-1 at 1 A g-1 , four times higher than reduced graphene oxide electrode (127.5 F g-1 )), superior cycle stability (the capacitance retention of 98.9% in 2 m KOH and 99.2% in 1 m H2 SO4 after 8000 cycles), and excellent energy density (42.8 Wh kg-1 at power density of 500 W kg-1 in 2 m KOH aqueous electrolyte). The results indicate the potential use of NG as graphene-based electrode material for energy storage devices.