Synergistic activation-doping strategy for constructing N/O/B/S Co-doped hierarchical porous carbon from wild jujube pit towards high-performance supercapacitors

Abstract

This study developed a synergistic activation-doping strategy using Wild Jujube Pits as a carbon source. The K₂CO₃/(NH₄)₂SO₄/H₃BO₃ ternary system synchronously modulates pore evolution and heteroatom doping, successfully constructing N/O/B/S-co-doped hierarchical porous carbon (JS1211). Characterisation results demonstrate that JS1211 possesses a high SSA of 1496 m² g⁻¹ with hierarchical porosity (micropores: 0.4–0.8 nm; mesopores: 2–10 nm). XPS analysis confirms uniform co-doping of N (7.55 at%), B (6.04 at%), S (0.56 at%), and O (15.78 at%), where pyridinic-N (49.4 %) and BC₂O (43.6 %) configurations dominate. DFT calculations reveal a three-tiered doping mechanism proceeding through structural distortion → electronic reconstruction → property optimisation. Electrochemical testing shows JS1211 delivers a specific capacitance of 411 F g⁻¹ at 0.5 A g⁻¹, with 81.75 % capacity retention at 20 A g⁻¹ and 97.31 % capacitance retention after 5000 cycles (Coulombic efficiency: 100.46 %). The assembled symmetric supercapacitor achieves an energy density of 12.85 Wh kg⁻¹ (Power density: 129.71 W kg⁻¹) in a 6 M KOH electrolyte, while retaining 7.85 Wh kg⁻¹ at a power density of 10,335 W kg⁻¹. This work provides new insights for developing biomass-derived high-performance supercapacitor electrodes.