Honeycomb-like N, S dual-doped porous carbons derived from pomelo peel by effective exogenous doping strategy for supercapacitor electrodes

Biomass has emerged as a pivotal precursor to synthesize supercapacitor electrode materials owing to its low-cost and plentiful resources. The optimization of heteroatoms and porous structures is believed to be a viable method to enhance the electrochemical properties of biomass-generated carbons. Herein, pomelo peel as a precursor using KOH as an activator and heteroatom dopants (urea and sodium sulfide) was successfully converted into N, S dual-doped porous carbons under the high temperature. The effective exogenous doping strategy realizes a high abundance of N/S heteroatoms, and KOH chemical activation promotes the development of nanopores and interconnected porosities. The resultant carbon CNS-800 with a high specific surface area of 1823.8 m² g⁻¹ and rich heteroatoms of N (2.51 wt%) and S (1.36 wt%) anticipately exhibits the outstanding electrochemical properties, including the excellent specific capacitance of 329.2 F g⁻¹ at 1 A g⁻¹ in a three-electrode (3E) system and the superb capacitance retention rate of 74.12 %. The fabricated CNS-800-based symmetric two-electrode (2E) supercapacitor demonstrates a good capacitance of 243.7 F g⁻¹ and excellent cycling stability, as well as a superb energy density of 14.3 Wh kg⁻¹. This work provides a compelling and cost-effective approach to transform biomass waste like pomelo peels into high-performance electrodes for supercapacitors.