Promising porous carbons derived from lotus seedpods with outstanding supercapacitance performance

Biomass-derived porous carbons are widely regarded as one of the most promising electrode materials for supercapacitors owing to their natural abundance and low-cost. Herein, we present a facile approach to synthesize promising porous carbons via a two-step fabrication process using lotus seedpods (LS) as the biomass precursor. Firstly, the LS is hydrothermally treated in a KOH aqueous solution. After filtration and drying, the hydrothermal product is directly subjected to simultaneous pyrolysis and activation, giving LS-derived porous carbon materials. The morphology, structure and textural properties of the carbon materials are investigated by scanning electron microscopy, transmission electron microscopy, and N2 sorption isotherms. The porous carbon prepared under optimal conditions exhibits a relatively high BET surface area of 1813 m(2) g(-1) and an average pore size of 3.30 nm. Such porous carbon shows outstanding capacitive performance (402 F g(-1) at 0.5 A g(-1)), good rate capability and excellent cycling stability (95.4% of capacitance retention after 10,000 cycles) in 6 M KOH electrolyte. More importantly, the as-assembled symmetric supercapacitor delivers a high energy density of 12.5 Wh kg(-1) at power density of 260 W kg(-1). (C) 2016 Elsevier Ltd. All rights reserved.