High-performance supercapacitors based on porous activated carbons from cattail wool

As electrode materials for supercapacitors, biomass-derived activated carbons attract much attention owing to their natural abundance and low cost. In this work, porous activated carbons are facilely synthesized from cattail wool using Ni(NO ₃) ₂·6H ₂O and KOH as co-etching agents. Compared with the carbons singly etched with KOH, these CWAC-x materials with hierarchical pores have much higher specific surface areas and exhibit much better capacitive performance. As for CWAC-10, the specific surface area and total pore volume are as high as 1581 m ² g ⁻¹ and 0.992 cm ³ g ⁻¹, respectively. For supercapacitor applications, CWAC-10 exhibits a high specific capacitance (314 F g ⁻¹ at 1.0 A g ⁻¹ in a three-electrode system), excellent cycling stability and high energy density (37.29 Wh kg ⁻¹ at a power density of 159.98 W kg ⁻¹ in a coin-type symmetric device). The enhanced electrochemical performance can be attributed to the unique structure and the existence of O and N elements.