Chitosan-derived N/B co-doped hierarchical porous carbon prepared using deep eutectic solvents and its application in Zn-ion hybrid supercapacitors

Abstract

Carbon materials are ideal materials for the electrodes of Zn-ion hybrid supercapacitors due to their high conductivity, large specific surface area, good chemical stability, and low cost. However, enhancing their specific capacity and addressing the challenges and costs associated with carbon cathode material preparation remain pivotal in research. Therefore, current research focuses on developing novel carbon-based positive electrodes that possess abundant electrochemical active sites and pseudocapacitance characteristics. In this regard, a novel approach is proposed in this study for the high-efficiency fabrication of N/B co-doped porous carbons (NBPCs) with an enhanced specific surface area (SSA) and abundant pore structures utilizing chitosan rich in nitrogen as the carbon precursor and a deep eutectic solvent (DES) as the activating agent. The as-prepared NBPCs exhibit a high SSA (1051.62 m² g⁻¹), large pore volume (0.81 cm³ g⁻¹), micropore volume (0.288 cm³ g⁻¹), and rich element contents (6.65 at% boron, 17.86 at% oxygen, and 7.81 at% nitrogen). When used as cathode materials for ZHSCs in 2 M ZnSO₄ electrolytes, the obtained NBPCs show a significantly high gravimetric capacitance of 143.03 W h kg⁻¹ at a current density of 0.25 A g⁻¹.