Crude fiber and protein rich cottonseed meal derived carbon quantum dots composite porous carbon for supercapacitor

Cottonseed meal (CM) contains abundant crude fiber and crude protein, which is a kind of high quality carbon precursor. Herein, CM is hydrothermal treated by H2SO4 solution to get the carbon quantum dots (CQDs) and hydrothermal pre-carbonization CM (HCM). The CQDs and HCM composite are carbonize-activated with K2CO3 and obtain the N, O, S self-doping porous carbon. CQDs with good crystallinity and abundant heteroatoms attach themselves to HCM, that increase the conductivity and heteroatoms contents of the obtained porous carbon. The prepared porous carbon possesses good conductivity, reasonable pore size distribution, large specific surface area and rich heteroatomic doping, which result in an ultrahigh specific capacitance of 477 F g−1 in 6 M KOH. Moreover, the assembled symmetric capacitor using a novel K2CO3-glycol-arginine deep eutectic solvent electrolyte displays a high voltage window of 2.0 V, superior energy density of 45.6 Wh kg−1 and a wide range of working temperatures.