High-Surface-Area Porous Carbon Flakes Derived from Boat-Fruited Sterculia Seeds for High-Energy-Density Aqueous Symmetric Supercapacitors

A new kind of N-doped porous carbon flake with a super high surface area of 3243.92 m(2) g(-1) was derived from a common biomass waste (boat-fruited sterculia seeds) by a facile low-cost pyrolysis and activation method. This particular biomass has a natural netlike structure consisting of interconnected polysaccharide chains rich in hydrophilic groups. We used the spongelike biomass gel as carbon precursor directly without a drying process and added some NaCl as the structure template, and were surprised to find that it is crucial for high surface area and the formation of two-dimensional materials. It is noted that the obtained materials possess a high specific capacitance (411.5 F g(-1) at 1 A g(-1)) and excellent cycling stability in aqueous electrolytes. Moreover, the assembled symmetric cell with has a wide voltage range of 2.0 V in 1 M Na2SO4 aqueous electrolyte, delivering a high energy density of 22.4 W h kg(-1) at 500 W kg(-1). Therefore, the outstanding electrochemical performance of the developed materials makes them promising candidates for high-performance supercapacitors.