Nitrogen-oxygen co-doped porous carbons prepared by mild potassium hydroxide activation of cicada slough for high-performance supercapacitors

摘要

Simultaneously achieving high specific energy/power remains a major challenge for supercapacitors. A mild KOH activation method is proposed to prepare N-O co-doped porous carbons (CPCKx) from cicada slough under low KOH/precursor mass ratio (1). Chitin and protein in cicada slough act as carbon sources, metal ions as catalytic templates to endow CPCKx with porosity and enhanced degree of order. The abundant heteroatom groups distributed uniformly in cicada slough serve as active sites for KOH activation to fabricate nanopores with narrow pore size distribution. CPCK0.7 possesses high surface area (2086 m(2) g(-1)) and suitable oxygen (10.16 at %) and nitrogen (1.42 at%) contents, while CPCK0.9 (e)xhibits higher surface area (2270 m(2) g(-1)) and superior conductivity (1477 S m(-1)). Consequently, CPCK0.7 and CPCK0.9 deliver excellent electrochemical performances in aqueous and ion liquid electrolytes, respectively, which are closely related with their surface wettability. The CPCK0.7 based symmetrical supercapacitor yields a high specific energy of 25.5 Wh kg(-1) at 223.0 W kg(-1) and outstanding rate capability (10.3 Wh kg(-1) at 10.1 kW kg(-1)) using Li2SO4 electrolyte. Notably, the supercapacitor based on CPCK0.9 delivers a remarkable specific energy of 72.1 Wh kg(-1) at 474.4 W kg(-1) and retains 30 Wh kg(-1) even at 15.1 kW kg(-1) in ionic liquid electrolyte.