Buckwheat husk-derived hierarchical porous nitrogen-doped carbon materials for high-performance symmetric supercapacitor

摘要

A facile one-step strategy is established to prepare nitrogen doped three-dimensional (3D) hierarchical porous carbon from buckwheat husk, in which the synchronous activation and nitrogen-doping is fulfilled via using KOH and urea. The obtained sample (BSCN-700) possesses an ultrahigh specific surface area of 2794.5m(2) g(-1) with a unique carbon frame. The electrochemical measurements indicate that the resultant BSCN-700 exhibits a high specific capacitance of 326F g(-1) at current density of 1A g(-1), with good rate capability (78.4% capacitance retention at 100A g(-1)) in 6M KOH electrolyte. Furthermore, the as-prepared sample was used to assemble a symmetric supercapacitor filled with 6M KOH electrolyte. As a result, the BSCN-700 symmetric supercapacitor displays a high energy density of 20.4 Wh kg(-1) at a power density of 699W kg(-1) and good cycling stability which retains 95% of the initial capacitance at 5A g(-1) after 5000 cycles.