Nitrogen and oxygen co-doped microporous carbons derived from the leaves of Euonymus japonicas as high performance supercapacitor electrode material

Bio-inspired nitrogen and oxygen heteroatom-doped porous carbons are prepared by facile pyrolysis of leaves of Euonymus japonicas (LEJ) with KOH activation. The pore textures of the carbons derived from LEJ (LEJCs) have been well controlled by adjusting the activation temperature. The obtained LEJCs possess large specific surface areas between 613 and 2071 m(2) g(-1) and moderate pore volumes of 0.281-0.872 cm(3) g(-1) with high micropore volume ratio of 74-96% and pore size distributions in the range of 0.5-2 nm. The optimized LEJC sample has 4.0 wt% N and 7.3 wt% O heteroatom-doped two-dimensional microporous structure as well as suitable specific surface area of 1268 m(2) g(-1) and pore volumes of 0.486 cm(3) g(-1) with the highest micropore volume ratio of 96% and main pore size distribution at 0.55 nm. The optimized LEJC material combining double layer and Faradaic redox electrochemical capacitance contributions, exhibits the max specific capacitance of 303 F g(-1) at 0.2 A g(-1), and 87% of the capacitance (264 F g(-1)) may be preserved when the current density increases to 40 A g(-1) in 6 M KOH aqueous electrolyte. A high cycle stability with 80% capacitance retention has been observed after 5000 charge-discharge cycles at 5 A g(-1). The max energy density of 15.2 Wh kg(-1) has been gotten at the power density of 60.3 W kg(-1), and a good energy density of 5.0 Wh kg(-1) can be found at the high power density of 8.6 kW kg(-1) in 6 M KOH. (C) 2015 Elsevier Inc. All rights reserved.