Iron-assisted regulation of microporosity and local carbon ordering in sugarcane bagasse-derived porous carbon for high-rate supercapacitors.

Achieving a balance among extensive microporosity, local carbon ordering, and surface functionality remains a central challenge in designing biomass-derived carbon electrodes because intensive activation can disrupt the sp2-carbon framework and remove heteroatoms. Here, sugarcane bagasse was converted into porous carbon through pre-carbonization followed by FeCl3-assisted KOH activation to examine how KOH dosage and activation temperature influence carbon structure and electrochemical performance at a fixed precursor/FeCl3 mass ratio of 1:1. Under matched KOH activation and acid-washing conditions, FeCl3 addition increased the Brunauer-Emmett-Teller surface area from 2038 to 3267 m2 g-1, decreased the Raman D-to-G band intensity ratio (ID/IG) from 1.04 to 0.95, and increased the surface nitrogen concentration from 0.27 to 1.17 at.%. Inductively coupled plasma optical emission spectrometry (ICP-OES) detected 0.0189 ± 0.0002 wt% residual Fe in acid-washed SBC-3-750, based on three technical readings from a single digest. Across three independent synthesis batches, the optimized electrode delivered 299.0 ± 12.8 F g-1 at 0.5 A g-1 and 191.0 ± 9.5 F g-1 at 20 A g-1, corresponding to 63.9 ± 0.7 % retention. A single long-duration test showed 97.3 % capacitance retention after 12,000 cycles. Symmetric devices delivered 24.4 ± 2.0 Wh kg-1 in 1 M Na2SO4 and 6.3 ± 0.3 Wh kg-1 in 6 M KOH, normalized to the total active-material mass of both electrodes. These findings support an Fe-associated structural effect but do not establish a unique catalytic pathway.