Nanostructured activated carbons for electrochemical double-layer capacitors were synthesized from depleted fullerene soot (DFS) via KOH activation. The structural and textural properties of the activated DFS were studied using transmission electron microscopy, X-ray diffraction, and nitrogen sorption. Activated DFS with high specific surface areas (SSAs) of up to 2,153 m2 g−1 and narrow pore size distributions (PSDs) was obtained by controlling the KOH/DFS ratio. The activated DFS exhibited excellent capacitive behavior, with a high specific capacitance of 250 F g−1 at a current density of 50 mA g−1 in a 6 M KOH electrolyte, and a high rate performance, with a capacitance retention of up to 80 % at a high scan rate of 200 mV s−1. Moreover, the activated DFS samples exhibited good electrochemical stability; high capacitance retention ratios of >90 % were obtained at a current density of 2,000 mA g−1 for 5,000 cycles with cell voltages of 0.9 and 1.0 V in a two-electrode system. The high electrochemical performance can be attributed to high SSAs, narrow PSDs, and nanoscale particle sizes, which facilitate the formation of electrochemical double layers and rapid ion diffusion.
