Balancing graphitization and defect density: N/S co-doped porous carbon from de-oiled camphor leaves for high-energy-density supercapacitors

Heteroatom doping is an effective strategy to break through the energy storage limitations of the conventional carbon-based supercapacitors and enhance the pseudocapacitive behavior. In this work, nitrogen and sulfur (N/S) co-doped porous carbon materials with controllable graphitized structures and abundant surface-active sites were synthesized via an in-situ doping method, using cellulase-pretreated de-oiled camphor leaves as the biomass precursor, potassium bicarbonate (KHCO₃) as the activator, and thiourea as the N/S source. N/S co-doping not only introduced numerous Faradaic active sites but also effectively balanced the graphitization degree and defect density of the material, significantly improving the pseudocapacitive contribution and overall capacitive performance. When the mass ratio of precursor, KHCO₃, and thiourea was 1:3:0.6, the resulting porous carbon electrode (PCNS-0.6) achieved a specific capacitance of 261 F·g −1 at the current density of 1 A·g −1 . At a scan rate of 10 mV·s −1 , the pseudocapacitive contribution reached 30.23%. Moreover, a symmetric supercapacitor assembled with PCNS-0.6 exhibited a capacitance retention rate of 89.5% after 10,000 cycles at 5 A·g −1 , and achieved an energy density of 13.63 Wh·kg −1 at a power density of 500 W·kg −1 , demonstrating excellent cyclic stability and promising potential for energy storage applications. This work provides an efficient synergistic modification strategy for the structural regulation and performance optimization of the biomass-derived carbon materials.