Preparation of Sargassum thunbergii derived porous carbon with enhanced capacitance performance: Synergistic effect of activating agent and CaCO3

A sustainable one-pot carbonization method has been designed to synthesize micro/meso hierarchical porous carbon. Hierarchically porous carbon with superior electrochemical capacitance and cycling stability was synthesized through the carbonization of Sargassum thunbergii biomass, employing K₂C₂O₄ as a chemical activator and waste eggshell-derived CaCO₃ nanoparticles as a hard template. The effects of K₂C₂O₂ activator dosage on the morphology, microstructure, and graphitization degree of porous carbon were systematically investigated under isothermal conditions. S_BET (specific surface area) of the obtained porous carbon ranges from 496.42 to 1246.33 m²∙g⁻¹, and the pore size is mainly distributed in the range of 0.5–5 nm. The sample STEK-2 prepared at an activation temperature of 700 °C with a mass ratio of 1:1:3 for Sargassum thunbergii, CaCO₃, and K₂C₂O₄ has the highest S_BET and V_total (total pore volume). The STEK-2 electrode obtained a specific capacitance of 299 F∙g⁻¹ in a three-electrode system in 6 M KOH electrolyte. When it was assembled as symmetric supercapacitors using STEK-2, the capacitance can maintain 97 % of the initial value after 10,000 cycles at a current density of 3 A∙g⁻¹.