Ingenious synthesis of chitosan-based porous carbon supercapacitors with large specific area by a small amount of potassium hydroxide

Chitosan has been widely studied in the preparation of carbon-based supercapacitor electrodes due to its environment-friendly characteristic and easy processing. However, most of the chitosan-based porous carbon preparation method was complicated and required some activators such as zinc chloride and potassium hydroxide (KOH), which were all not conducive to environmental and equipment protection. Herein, we have successfully used a one-step carbonization method to prepare N-doped hierarchical porous carbon by systematically combining a small amount of KOH with magnesium acetate. The phenomenon was confirmed by observing scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption isotherms. The porous carbon showed a high specific surface area of ~2737 m2 g−1, and its nitrogen content was up to 2.39%. Electrochemical data exhibited that the chitosan-based carbon electrode could achieve an outstanding gravimetric capacitance of 300.5 F g−1 at a current density of 0.5 A g−1. After cyclic charging and discharging 5000 times at a current density of 5 A g−1, the specific capacitance retention rate was 92.94%. As an assembled symmetrical supercapacitor, with 6 M KOH as the electrolyte, when the power density was 250–4991 W kg−1, the corresponding energy density was 7.3–6.1 Wh kg−1. Thus, these chitosan-based porous carbon electrodes exhibited excellent electrochemical properties. Particularly, the strategy to prepare porous carbon would provide successful experiences for designing bio-polymers porous carbon.