Synthesis of cigarette filter-derived activated carbon using various activating agents for flexible capacitive supercapacitors

Activated carbon (AC) with low-cost, high surface area and pore volume properties is common active material of commercial supercapacitor (SC). Producing AC using cigarette filters (CF) cannot only reduce serious CF pollution but also decrease ingredient costs. Also, activating agents have been reported to play important roles on energy storage ability of home-made AC. In this work, it is the first time to use CF to synthesize AC with ZnCl₂, KOH and H₃PO₄ as activating agents. The CF-derived AC activated by KOH (CAC-KOH) shows abundant functional groups, larger surface area, well-constructed pore structure and suitable defect-to-graphene intensity. The CAC-KOH electrode achieves the largest specific capacitance (C_sp) of 106.5 F/g at 0.5 A/g, while the CF-derived AC electrodes fabricated using ZnCl₂ and H₃PO₄ show smaller C_sp values of 4.2 and 9.4 F/g, respectively. The symmetric SC assembled using CAC-KOH electrodes presents a maximum energy density of 5.15 Wh/kg at 325 W/kg and a C_sp retention of 73 % after 11,000 charge/discharge cycles. Synthesizing AC with polluted CF successfully opens new blueprints for using wastes to produce efficient active material. It is expected to further enhance energy storage ability of wastes-derived AC by refining the activation process in near future.