KHCO₃ Chemical-Activated Hydrothermal Porous Carbon Derived from Sugarcane bagasse for Supercapacitor Applications

The reuse of waste biomass resources had become a hot topic in the sustainable development of human society. Biomass was an ideal precursor for preparing porous carbon. However, due to the complexity of biomass composition and microstructure, the quality reproducibility of biomass porous carbon was poor. Therefore, it was of great significance to develop a reliable method for preparing porous carbon from biomass. In this paper, the activated hydrothermal porous carbon was prepared by a combination of hydrothermal carbonization treatment and KHCO₃ mild activation. The hydrothermal carbonization treatment could complete the morphology adjustment and iron doping of the carbon in one step, and the mild activation of KHCO₃ could activate the porous carbon while maintaining the spherical morphology. Fe-modified porous carbon with carbon ball/nanosheet structure prepared from bagasse exhibited a high surface area (2169.8 m²/g), which facilitated ion/electrolyte diffusion and increased accessibility between surface area and electrolyte ions. Therefore, bagasse derived activated porous carbon had good specific capacitance (315.2 F/g at 1 A/g) and good cycle stability, with a capacitance loss of only 5.8 % after 5000 charge-discharge cycles, and the Na₂SO₄-based device showed the maximum energy density of 13.02 Wh/kg. This study showed that the combination of hydrothermal treatment and mild activation provided an effective way for the conversion of waste biomass into high-performance electrode materials.