Agarose-derived carbon aerogels with defect-rich curved carbon domains for fast and stable supercapacitors

Beyond pore architecture, local carbon configurations of porous carbons, particularly structural defects and curved carbon domains, play crucial roles in regulating ion adsorption and charge-transfer kinetics in high-rate supercapacitors. However, developing an effective synthetic route that simultaneously constructs hierarchical porosity and tailors defect-rich curved carbon frameworks remains challenging. Herein, agarose-derived porous carbon aerogels were fabricated via Zn-assisted carbonization and CO₂ activation. Zn species helped preserve the three-dimensional network during pyrolysis, while CO₂ activation simultaneously induced pore development, defect enrichment, carbon-layer curvature, and surface deoxygenation. The optimized sample exhibits a hierarchical micro/mesoporous structure, abundant defects, curved carbon layers, and relatively low oxygen content. As a result, it delivers a specific capacitance of 259 F g^-1 and a high capacitance retention of 84.0% from 0.5 to 5 A g^-1, together with a short relaxation time constant of 0.78 s. Kinetic analysis indicates a predominantly capacitive-controlled process, while density functional theory calculations reveal that defective curved carbon possesses the lowest adsorption energy toward K⁺, favoring rapid ion adsorption. The assembled symmetric device further achieves 5.6 Wh kg^-1 at 2500 W kg^-1 with 97.4% capacitance retention after 10,000 cycles.