Scalable synthesis of N, O co-doped hierarchical porous carbon for high energy density supercapacitors.

[Display omitted] • The chitin derived hydrochar at 300 °C has a high N content (10.7 wt%) and thermal stability. • N, O co-doped hierarchical porous carbon with high specific surface area and abundant N, O heteroatoms was successfully prepared. • Abundant N, O heteroatoms contribute to additional pseudocapacitance. • The assembled symmetric supercapacitors present an ultrahigh energy density of 30.8 Wh kg−1 at 180 W kg−1. Rational design of hierarchical porous architecture with abundant pseudocapacitive sites is highly desirable for carbon electrode materials. However, the lengthy production process and high economic input limit its broader application. Herein, we successfully prepared N, O co-doped hierarchical porous carbon (NOHC) through hydrothermal carbonization (HTC) of chitin biomass with the assist of NH 4 Cl and subsequent carbonization with NaNH 2. The optimal NOHC600 exhibits a remarkable hierarchical porous structure and an ultrahigh specific surface area (SSA) of 2555 m2 g−1. Furthermore, it showcases a significant content of N, O co-doping, thereby providing abundant defects and additional active sites for ion adsorption. The aforementioned characteristics ensure outstanding capacitance performance of NOHC600. In the three-electrode system, NOHC600 exhibits a remarkable specific capacitance of up to 455 F g−1 at a current density of 0.5 A g-1. The symmetric supercapacitors (SCs) based on NOHC600 achieve an impressive energy density of 30.4 Wh kg−1 at a power density of 180 W kg−1. Moreover, the all-solid-state NOHC600 microsupercapacitors (MSCs) demonstrate an exceptional areal capacitance of 78.2 mF cm−2 and an areal energy density of up to 10.8 μWh cm−2. Accordingly, this facile and scalable strategy shows a great potential for producing high-heteroatom-doped porous carbon materials from chitin biomass, which can be applied in practical energy-related applications. [ABSTRACT FROM AUTHOR]