Dual‐template Synthesis of Hierarchical Porous Carbon and Its Application in Electrical Double‐layer Capacitors

Hierarchical porous carbons (HPCs) with tailored pore structure were fabricated via direct carbonization of a precursor consisting of agar and acetates in an inert atmosphere. The agar served as the carbon source and curing agent, while potassium acetate and calcium acetate were used to create micropores and mesopores, respectively. The morphology and structural features of the HPCs were characterized, and the electrochemical properties were estimated in a three-electrode system with 6 M KOH as the electrolyte. The resulting HPCs possess a developed pore structure and concentrated pore size distribution (focused at 0.4 and 4 nm), and exhibit typical electrical double-layer capacitive behaviour. Specially, the HCP-2 owns a large specific surface area of 1441.65 m(2)/g and excellent electrochemical properties, including a favourable specific capacitance (235 F/g at 1 A/g), good rate capability (capacitance retention rate of 88.1% at 20 A/g), and impressive long-term cycling stability (90.6% retention of initial capacitance after 3000 cycles).