High-Performance Supercapacitor Electrode Materials from Chitosan via Hydrothermal Carbonization and Potassium Hydroxide Activation

Nitrogen-rich porous carbonaceous materials suitable for supercapacitor applications can be synthesized directly from chitosan using a hydrothermal treatment (250 °C, 14 h) that is followed by chemical activation of the carbonized solids with KOH (ca. 800 °C, 2 h). The synthesized chitosan-derived carbonaceous materials (CDCMs) had high specific surface area (ca. 2200 m² g⁻¹), large pore volume (ca. 1.36 cm³ g⁻¹), and high nitrogen content (ca. 6.3 %). When a current density of 0.5 A g⁻¹ was applied to CDCM-800 obtained at an activation temperature of 800 °C, specific capacitances of 231 and 305 F g⁻¹ were achieved for 0.5 m K₂SO₄ and 6 m KOH aqueous electrolytes, respectively. Capacitances of 154 and 198 F g⁻¹ were retained for the respective electrolytes at 20 Ag⁻¹. CDCM-800 had an energy density of 8.5 Wh kg⁻¹ corresponding to a specific power of 1 kW kg⁻¹ at 20 A g⁻¹ in 6 m KOH aqueous electrolytes. The prepared carbonaceous materials retained 99 % of their properties for over 3000 cycles at 1 A g⁻¹ in 0.5 m K₂SO₄. The nitrogen-rich nanoporous carbonaceous materials have wide application in energy, electrical, chemical, analytic, separation, and catalysis.