Efficient Fabrication of Hierarchical Porous Carbon Fibers with Tunable Mesopores from Discarded Aramid for Supercapacitors

Template-free synthesis of advanced supercapacitor carbon with tunable interpenetrating micromesoporous structures remains a formidable challenge. Herein, porous carbon fibers with tunable mesopores were fabricated that were derived from discarded aramid fibers by H 3 PO 4 -assisted KOH activation without a template. The structural design of porous carbon fibers was achieved by utilizing the dehydration condensation reaction of H 3 PO 4 with the amide groups in the aramid chain segments, which developed primary pores of porous carbon fibers and further facilitated K + etching and embedding during subsequent KOH activation. The derived porous carbon fibers exhibited extremely tremendous specific surface area, abundant tunable mesopores, and N/O enriched surface. Benefiting from the synergy of the unique hierarchical porous structure and surface characteristics, the optimized porous carbon fiber provided an extremely high specific capacitance of 434.8 F g –1 at 0.2 A g –1 in a 6 M KOH electrolyte and excellent rate performance. Furthermore, in a 1 M Na 2 SO 4 electrolyte, the assembled symmetric aqueous supercapacitor device displayed an ultrahigh energy density of 25.26 Wh kg –1 at a corresponding power density of 450 W kg –1, as well as remarkable cycling stability.