Abstract
N-doped porous carbon nanospheres were fabricated directly by pyrolyzing chitin nanogels, which were facilely prepared by mechanical agitation induced sol-gel transition of chitin solution in NaOH/urea solvent. The resulting carbon nanospheres displayed ordered micropores (centered at ∼0.6 nm) and high BET surface area of up to 1363 m(2) g(-1), which is substantially larger than that of the carbons from raw chitin (600 m(2) g(-1)). In addition, the carbon nanospheres retained a nitrogen content of 3.2% and excellent conductivity. Consequently, supercapacitor electrodes prepared from the carbon nanospheres pyrolyzed at 800 °C showed a specific capacitance as high as 192 F g(-1) at a current density of 0.5 A g(-1) and impressive rate capability (81% retention at 10 A g(-1)). When assembled in a symmetrical two-electrode cell, N-doped porous carbon nanospheres demonstrated excellent cycling stability both in aqueous and organic electrolytes (95% retention after 10 000 cycles at 10 A g(-1)), together with outstanding energy density of 5.1 W h kg(-1) at the power density of 2364.9 W kg(-1). This work introduces a novel and efficient method to prepared N-doped porous carbon nanospheres directly from chitin and demonstrates the great potential of utilization of abundant polymers from nature in power storage.