Sustainable nitrogen-rich hierarchical porous carbon nest for supercapacitor application

Chitosan has high synthetic flexibility, making it a promising nitrogenous bioresource for industrial applications. Nitrogen-rich hierarchically porous carbon (NHPC) was successfully synthesized by hydrothermal carbonization and self-activation of a chitosan-transition metal ion (Zn 2+ ) complex. The N 2 adsorption-desorption isotherm revealed that the as-made NHPC had large specific surface area (1067 m 2  g −1 ) and a unique hierarchical pore structure (0.6–6.4 nm). Scanning electron microscopy (SEM) indicated a 3D finely interconnected nest architecture for NHPC. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the nitrogen atoms in the chitosan were protected by coordination with zinc ions , and most of them were still retained in the carbon matrix (6.36 at%) after high temperature activation. Electrochemical measurements exhibited that NHPC delivers a high specific capacitance (228.7 Fg −1 at 1 A g −1 ), impressive rate capability (the specific capacitance at 20 A g −1 was 174 Fg −1 , maintaining 74.6% of the initial capacitance at 0.5 A g -1 ), and outstanding long-term cycling stability (98.3% retention after 5000 cycles), together with excellent energy density of 25.7 Wh kg -1 at the power density of 500 W kg -1 . This study offers a novel strategy for synthesizing NHPC as one of the desirable electrode material candidates for energy storage.