Breaking the hemicellulose barrier for the preparation of high-performance porous carbon for supercapacitors and Zinc-Ion capacitors

Abstract

In recent years, biomass-based carbon supercapacitors and zinc-ion capacitors (ZICs) have garnered significant interest from researchers. Traditional methods for preparing porous carbon (PC) typically involve a carbonization-activation process. PC prepared through this method generally exhibits issues such as low specific surface area (SSA) and poor pore structure, which result from the inherently compact structure of the biomass. Therefore, this study proposes a novel preparation method, namely the hydrothermal modification-carbonization-activation process. This new process disrupts the cross-linked structure of the biomass, resulting in PC with a well-developed pore structure and a large SSA. Experimental results show that the unmodified samples have a low SSA, while the SSA of the PC produced from hydrothermal modification is significantly improved. The best-performing sample exhibited a high SSA of 2985.60 m²/g. In the three-electrode system with 6 M KOH, the sample achieved a specific capacitance of 339.8F/g at 0.5 A/g. In the organic electrolyte, its symmetrical supercapacitor achieved an energy density of 31.83 Wh/kg at 337.5 W/kg. Furthermore, it demonstrated good capacitance retention in both aqueous and organic electrolytes, with values of 98.0 % and 100 %, respectively. The assembled ZICs exhibited a high specific capacitance of 146.3 mAh/g at 0.1 A/g. Additionally, the experimental results indicate that the SSA of the pivotal factor determining the final SSA of the PC. This novel approach, which regulates the SSA of the PC by adjusting the SSA of the biochar, offers valuable insights for the future preparation of biomass-derived PC.