One-step chemical activation facilitates synthesis of activated carbons from Acer truncatum seed shells for premium capacitor electrodes

Activated carbons were produced from Acer truncatum seed shells with KOH activation in one step (direct activation) or two steps (activation preceded with carbonization). The effects of activation mode and temperature on the surface/physicochemical properties and electrochemical characteristics of the resulting activated carbons were thoroughly investigated. One-step activation at 800 °C outperformed other operating conditions and the resulting activated carbon (OAAS-800) featured a large surface area of 2210.7 m² g^–1 and a total pore volume of 1.23 cm³ g⁻¹. The OAAS-800 based capacitor delivers a high specific capacitance of 361 F g⁻¹ at 0.5 A g⁻¹ in a 6 mol L⁻¹ KOH electrolyte, 82% capacitance retention after increasing current density from 0.5 to 20 A g^–1, and excellent cycle stability (98.6% capacitance retention after 10,000 cycles). The OAAS-800-based symmetric supercapacitor could offer a superior energy density of 27.78 W h kg^–1 at 250 W kg^–1 power density. The excellent performance was attributed to an interconnected three-dimensional porous structure. The simple yet very effective one-step activation opens up a new avenue for the production of high-performance supercapacitor electrode materials from low-cost oilseed plant residues.