One-step carbonization strategy of freeze-dried chitosan to prepare Nitrogen-Oxygen co-doped porous carbon supercapacitors with ultra-large specific surface area

Biomass-derived porous carbon materials were widely used in the preparation of supercapacitors due to their excellent electrical conductivity and large specific surface area. However, much research on the preparation process still involved pre-carbonization and high-temperature cracking. The preparation process was complicated and energy-consuming, which largely limited the development of biomass-based supercapacitors. Here, the chitosan gel was first obtained by a freeze-dried method, and then it was immersed into potassium hydroxide (KOH) solution and got the carbon precursor. Finally, a simple one-step carbonization process successfully prepared its hierarchical N-doped porous carbon (NPC) material. The N2 isothermal adsorption–desorption test and X-ray photoelectron spectroscopy (XPS) analysis showed the prepared NPC material had a specific surface area of 2787.47 m2 g−1 and an N content of 4.68 %. The electrochemical performance test showed that the prepared NPC material had a specific capacitance of 253F g−1 (0.5 A g−1) in 6 M KOH electrolyte under the three-electrode system. When assembled as an asymmetrical supercapacitor, the energy density was 5.83 Wh kg−1 at a power density of 4997.1 W kg−1 in a 6 M KOH electrolyte. Particularly, this study provided a simple strategy for synthesizing NPC materials with excellent properties.