Nitrogen-doped hierarchical porous carbon derived from a chitosan/polyethylene glycol blend for high performance supercapacitors

Abstract

Nitrogen-doped hierarchical porous carbon (NHPC) materials were synthesized by using a chitosan/polyethylene glycol (PEG) blend as raw material through a facile carbonization–activation process. In this method, chitosan was used as a nitrogen-containing carbon precursor, low cost and large-scale commercial PEG was employed as a porogen. The physical and electrochemical properties of the resultant NHPC were affected by the ratio of chitosan and PEG. The sample obtained by the ratio of 3 : 2 exhibits a high specific surface area (2269 m² g⁻¹), moderate nitrogen doping (3.22 at%) and optimized pore structure. It exhibits a high specific capacitance of 356 F g⁻¹ in 1 M H₂SO₄ and 271 F g⁻¹ in 2 M KOH at a current density of 1 A g⁻¹, and over 230 F g⁻¹ can be still retained at a high current density of 20 A g⁻¹ in both electrolytes. Additionally, the assembled symmetric supercapacitors show an excellent cycling stability with 94% (in 1 M H₂SO₄) and 97% (in 2 M KOH) retention after 10 000 cycles at 1 A g⁻¹. These results indicate that the chitosan/PEG blend can act as a novel and appropriate precursor to prepare low-cost NHPC materials for high-performance supercapacitors.