In-situ synthesis of N, S sites activated porous carbon materials derived from Platycodonis Radix residue for symmetrical supercapacitor

The development of biomass carbon materials for green energy storage devices using low-cost, environmentally friendly methods has emerged as a promising strategy to alleviate the environmental impact of waste resources. This study focuses on the in-situ preparation of N, S sites activated porous carbon (N, S-PRC) materials through carbonization and KOH activation of Platycodonis Radix residue. By adjusting the amount of KOH, N, S-PRC materials with a significant specific surface area and diverse pore structures can be synthesized. This straightforward approach can also be applied to create various types of porous carbon electrodes using different types of herb residues. The optimized N, S-PRC-4 electrode exhibits a good specific capacitance of 486.0 F g-1 at a current density of 0.5 A g-1 and maintains a cycling durability of 91% over 10,000 cycles. Additionally, a symmetrical supercapacitor constructed by N, S-PRC-4 electrode achieves an energy density of 15.4 Wh kg-1 at a power density of 250 W kg-1 and retains a cycling stability of 90.2% after 10,000 cycles at 5 A g-1. These impressive electrochemical performances are ascribed to the unique three-dimensional structure and the abundant presence of N and S elements. This study presents a valuable reference for utilizing various Chinese medicine residues from different medicinal parts in energy storage devices.