From weed to N/O/S co-doped honeycomb-like porous carbon for high-performance supercapacitors: a facile and friendly one-step carbonization

Recent research interest has increased in the production of heteroatoms-doped porous carbon with controlled morphology from biomass. However, there is still a significant challenge in resolving alkaline solutions that cause equipment corrosion and devising a simple and adaptable approach. In this study, N/O/S co-doped honeycomb-like porous carbons were synthesized from a widely cultivated annual weed (Hemistepta Iyrata Bunge) using a simple and eco-friendly method. The sodium hydroxide (NaOH)/urea system was utilized as the pore-forming agent and cellulose solvent, with urea as the nitrogen source. By varying the activation temperature, the as-prepared porous carbon has a high specific surface area (709 m2 g−1), a large total pore volume (0.44 cm3 g−1), and a high heteroatom content of 6.20 at% nitrogen and 8.12 at% oxygen. The prepared porous materials were evaluated as electrodes for supercapacitors. The product (HIB-PHC-750 °C) exhibited a high specific capacitance (353.6 F g−1 at 0.2 A g−1) at a carbonization temperature of 750 °C. Additionally, the HIB-PHC-750 °C-based symmetric device with a wide voltage range of 2.0 V possessed a desirable energy density of 44.22 Wh kg−1 at 500 W kg−1. Moreover, the HIB-PHC-750 °C also demonstrated outstanding cycling stability with 98.2 % capacitance retention after 10,000 cycles. This research provided a facile and favorable alternative method for preparing N/O/S co-doped honeycomb-like porous carbon for electrochemical energy storage devices.