Hierarchical Nanoporous C/C Composite from Humic Fulvic Acid and Sulfonated Pitch for High‐Energy‐Density EDLC Electrodes

Abstract As a new type of energy storage device, electric double layer capacitors (EDLCs) possess fast charge/discharge speed and good cycling stability. However, the low energy density and high production cost of EDLC electrodes are still big challenges. Herein, a hierarchical nanoporous C/C composite is synthesized by chemical recombination and subsequent activation strategy from low‐cost carbon resources, namely renewable humic fulvic acid (FA) and industrial sulfonated pitch (SP). Profiting from the abundant polycyclic aromatic hydrocarbons in SP and plentiful oxygen‐containing groups in FA, the resultant nanoporous C/C composite has both high e‐conductivity and high specific surface area (SSA). Thus, this porous C/C composite can be directly fabricated as EDLC electrode without any conductive agent. By fully exploiting the synergistic effect between high e‐conductivity and high SSA, it shows excellent electrochemical stability in EMIMBF₄ ionic liquid electrolyte. Furthermore, it possesses a higher specific gravimetric capacitance (117 F g⁻¹) than that of pure FA‐based porous carbon (92.5 F g⁻¹) at a current density of 1 A g⁻¹. More importantly, the maximum energy density can be as high as 55.4 Wh kg⁻¹, largely better than commercial activated carbon.