Hierarchically porous carbon derived from chaenomeles cathayensis seeds for high-performance supercapacitors

Abstract

Biomass-derived activated carbon (BAC) materials are ideal electrode candidates for supercapacitors due to their eco-friendliness, cost-effectiveness, and robust physicochemical stability. The development of porous carbons with high specific surface area and energy density necessitates optimized biomass selection and advanced carbonization-activation strategies. Herein, Chaenomeles cathayensis seeds were employed as carbon precursors to synthesize oxygen self-doped porous activated carbons (CSAC) through sequential carbonization and chemical activation using K₂CO₃, KOH, or NaOH. Distinct pore-forming mechanisms were observed: K₂CO₃ preferentially generates micropores, NaOH favors mesopore formation, while KOH creates hierarchical micro-mesoporous architectures. Such hierarchical porosity synergistically facilitates rapid electrolyte ion diffusion through mesopores and provides abundant adsorption sites via micropores. Consequently, CSAC-KOH demonstrates superior electrochemical performance, achieving a specific capacitance of 378 F g⁻¹ at 0.5 A g⁻¹, superior rate capability (249 F g⁻¹ at 20 A g⁻¹), and exceptional cycling stability (99.5% retention after 5000 cycles). The symmetric supercapacitor (SC) fabricated with CSAC electrodes and KOH electrolyte exhibits specific capacitance values of 65.4 F g⁻¹ (0.5 A g⁻¹) and 40 F g⁻¹ (5 A g⁻¹). Meanwhile, the Na₂SO₄-based SC achieves enhanced energy density (11.3 Wh kg⁻¹ at 490 W kg⁻¹) owing to its expanded voltage window (1.4 V), demonstrating the critical role of electrolyte selection in optimizing energy storage performance. This work not only advances the understanding of activator-biomass interactions but also provides a sustainable pathway for valorizing medicinal plant waste into high-performance energy storage materials.