Chemical exfoliation synthesis of N, O-doped tea Saponin-derived carbon for high-performance electrochemical electrodes

Porous carbon materials represent an ideal cathode material system for supercapacitors. To enable their scalable production, it is imperative to develop green synthesis methodologies as sustainable alternatives to conventional corrosive KOH activation processes. However, a significant challenge persists with most mild activating agents, which exhibit insufficient activation efficiency. This limitation detrimentally impacts the resulting materials, manifesting as reduced specific surface areas and compromised capacitive performance. Herein, we propose a chemical exfoliation method using KHCO₃ as a mild activating agent and tea saponin from the waste of camellia oleifera seeds after oil extraction as an inexpensive precursor. Urea assists in increasing the decomposition temperature of KHCO₃ and initiates an additional second step of gas stripping, transforming the material morphology from chunks to porous carbon sheets. This increases the specific surface area from 210 m² g⁻¹ to 1727 m² g⁻¹ and boosts the total pore volume from 0.182 cm³ g⁻¹ to 1.3342 cm³ g⁻¹. Additionally, the proper incorporation of N- and O- containing materials enhances the mass and charge transfer during the reaction process. The sample TSUK-700 exhibits higher specific capacitance and energy density, maintaining high stability (83 %) even after 10,000 cycles. Additionally, the TSUK-700 electrode shows a high electrosorption capacity for Cu⁺, reaching up to 404 mg g⁻¹. Therefore, this study provides a feasible idea for the resource utilization of biomass waste and the application of low-cost preparation of high-performance carbon materials.