An environmentally friendly process to derive N/O/S-codoped porous carbon from biomass waste with high yield for high performance supercapacitor

Plant ash and eggshells are explored to serve as natural activation agent and template to prepare N, O, and S co-doped carbon (KDPC) with porous structure from biomass - Descurainia sophia seeds. The obtained KDPC-20-600 shows a high yield of 75 % and a relatively high specific capacitance of 250.5 F g−1 at 0.5 A g−1 in 2 M KOH, which maintains 232.8 F g−1 at 1.0 A g−1, superior or comparable with commercial active carbon. Also, the KDPC-20-600 demonstrates a long-term cycling life with a capacitance retention of 99.0 % after 10,000 cycles. Furthermore, the KDPC-20-600-based symmetric supercapacitor displays a high energy density of 24.8 Wh kg−1 at 1050 W kg−1 in 1 M Na2SO4. The findings indicate that environmentally friendly agents (e.g., plant ash, eggshells) can substitute harsh chemicals (e.g., KOH, H3PO4) to synthesize porous carbon from biomass materials in-situ doped with heteroatoms. Therefore, this cost-effective, environmentally friendly and sustainable process to obtain porous carbon will shed light on the development of electroactive materials for energy storage and conversion devices.