Rapid synthesis of chitin-based porous carbons with high yield, high nitrogen retention, and low cost for high-rate supercapacitors

It is a great challenge to simultaneously achieve high yield, high nitrogen retention, and low cost for chitin-based porous carbons (PCs) while obtaining highly porous structure. Herein, copper (II) chloride dihydrate (CuCl2 2H(2)O) is innovatively used as the microwave absorber and also porogen for direct synthesis of PCs from chitin via microwave heating. A very short duration of 10 minutes is achieved for this synthesis, because microwave irradiation renders a rapid heating rate of 126 degrees C min(-1) during the initial 5 minutes. In addition, the melted CuCl2 wraps the chitin to preserve its overall structure during synthesis, thus obtaining a yield as high as 36% and a nitrogen retention up to 5.2%. Furthermore, a low temperature of about 600 degrees C that triggers the redox reactions of CuCl2 into Cu to achieve well-developed porous structure (specific surface area up to 1535 m(2) g(-1)) is observed, suggesting a merit of low cost for this synthesis. The PC-based electrode exhibits not only a high specific capacitance of 227 F g(-1) at 0.5 A g(-1) in 6 mol L-1 KOH electrolyte but also a good rate capability with a high capacitance retention of 67.7% even at an ultra-high current density of 50 A g(-1). Owing to these promising capacitive performances of PCs, the fabricated supercapacitor can remain 70.1% of the energy density when the power density was dramatically increased by 20 times.