Polytetrafluoroethylene-assisted removal of hard-template to prepare hierarchically porous carbon for high energy density supercapacitor with KI-additive electrolyte

Abstract A hierarchically porous carbon (HPC) is prepared via a facile hard-templating method using silica as a template, which is thoroughly removed by an in-situ polytetrafluoroethylene (PTFE) pyrolytic process without further post treatment. The Brunauer-Emmett-Teller specific surface area for HPC can reach up to 664 m2 g−1. The usage of PTFE and carbon precursor (glucosamine) lead to F, N co-doping on HPC. Electrochemical measurements show that HPC possesses a much higher specific capacitance (1161 F g−1) in a KI-additive electrolyte (H2SO4 + KI) than that (183 F g−1) in H2SO4 electrolyte due to the presence of oxidation states of I species such as IO3ˉ and I3ˉ, as confirmed by X-ray photoelectron spectroscopy (XPS), which can bring about superior pseudocapacitance by redox reaction. Furthermore, the operation voltage for the symmetric supercapacitor assembled by the as-prepared HPC can reach up to a much higher value of 1.7 V in KI-additive electrolyte compared with that in H2SO4 electrolyte. Marrying high operation voltage and high specific capacitance, the assembled supercapacitor can deliver a high energy density of 78.8 Wh kg−1 under a high-power output of 680 W kg−1.