Fabrication of porous carbon nanosheets via urea-promoted activation of potassium citrate for enhanced supercapacitor performance

• This study presents a sustainable method for synthesizing sodium humate-based porous carbon materials. • Pyridine-N acts as a key pore promoter, enhancing surface area and nanosheet formation. • Varying potassium citrate and activation temperature modulates C=O and pyrrole-N concentrations. • NHPC-750-3 achieves a surface area of 1749.96 m 2 /g and a specific capacitance of 310.1 F/g. • The NHPC-750-3//NHPC-750-3 supercapacitor delivers an energy density of 12.91 Wh/kg at 150 W/kg. Porous carbon materials, characterized by a high specific surface area and adjustable pore structure, serve as excellent electrode materials for supercapacitors. However, conventional production processes typically rely on large quantities of corrosive KOH as an activator, presenting significant challenges to sustainable development. Furthermore, some newly introduced green activators exhibit limited practical applications due to the underdeveloped pore structure resulting from low activation efficiency. In this study, we introduce an innovative method for synthesizing sodium humate-based porous carbon materials via the urea-promoted activation of potassium citrate, elucidating the underlying mechanisms involved. Notably, pyridine-N functions as the primary pore promoter, facilitating gas stripping and triggering secondary gasification reactions, which not only enhance the specific surface area of the carbon material but also promote the formation of nanosheets. Furthermore, varying the dosage of potassium citrate and the activation temperature allows for the modulation of C=O and pyrrole-N concentrations. The optimized material, NHPC-750-3, exhibits an exceptional specific surface area of 1749.96 m 2 /g and increased concentrations of C=O and pyrrole-N, showcasing remarkable electrochemical performance with a specific capacitance of 310.1 F/g at 0.5 A/g. The symmetric supercapacitor NHPC-750-3//NHPC-750-3 achieves a noteworthy energy density of 12.91 Wh/kg at 150 W/kg. These results offer essential insights for developing high-performance, eco-friendly electrode materials for supercapacitors.