Nitrogen and phosphorus co-doped silkworm-cocoon-based self-activated porous carbon for high performance supercapacitors

N/P co-doped porous carbon is prepared from biomass (silkworm cocoon) and natural product (phytic acid) by an eco-friendly self-activation approach. Owing to the rational pore structure, and abundant pseudocapacitive active sites of heteroatom doping, the prepared Cheese-brick-like porous carbon presents outstanding performances. The optimized S2 sample delivers both high gravimetric capacitance and volumetric capacitance of 317 F g−1 (482 F cm−3) at 1 A g−1, and an impressive capacitance of 159 F g−1 (242 F cm−3) at a high current density of 50 A g−1 in 1 M H2SO4. Also, the thick electrode (10 mg cm−2) can deliver a high areal capacitance up to 2.44 F cm−2 at 10 mA cm−2 and 1.29 F cm−2 at 500 mA cm−2. Additionally, the porous carbon based flexible symmetric supercapacitor (1.4 V) can deliver a remarkable 19.6 Wh kg−1 (29.8 Wh l−1) at 350 W kg−1, and 9.6 Wh kg−1 (14.6 Wh l−1) at 17500 W kg−1, respectively, as well as outstanding cyclic longevity (~98% capacitance retention after 10000 cycles). These attractive performances enable a wonderful potential of our porous carbon applied in supercapacitors for wearable electronics and other energy storage devices.