Fabrication of self-doped aramid-based porous carbon fibers for the high-performance supercapacitors

• A facile and efficient strategy is provided for the high-quality utilization of discarded aramid fibers. • Hierarchical porous carbon fibers with N/O enriched surface is obtained by pyrolysis and KOH activation process. • The electrode exhibits an ultra-high specific capacitance. • The symmetrical supercapacitor shows a high energy density in Na 2 SO 4 electrolyte. The development of novel and efficient electrode materials is crucial to the energy storage effectiveness of supercapacitors. Herein, a facile approach to obtain N and O self-doped hierarchical porous carbon fibers (PCFs) derived from discarded aramid fibers for high performance supercapacitor via pyrolysis coupled with KOH activation was proposed. The as-prepared PCFs have ultra-high specific surface area, well-developed micropore-mesopore structure and N/O enriched surface, resulting in superior electrochemical performance of the supercapacitor. Among the resultant samples prepared at different alkali/carbon ratios, the PCF-3 exhibited the largest specific capacitance of 390.3 F g -1 at a current density of 1 A g −1 in 6 M KOH. The as-assembled PCF-3 based symmetric supercapacitor device delivered an energy density up to 25.7 Wh kg −1 at the corresponding power density of 1000 W kg −1 in 1 M Na 2 SO 4 . Meanwhile, high energy and power densities were also achieved in 6 M KOH and CMC-Na/Na 2 SO 4 gel electrolyte. This work provides a simple strategy for fabricating high-performance supercapacitor electrode materials, and enables the recycling of discarded aramid fibers.