S/N/O co-doped lotus root-like porous carbon with high microporosity for aqueous supercapacitors

The superior pore structure is essential for improving the charge storage capacity of capacitive carbon, in which micropores mainly provide charge adsorption sites and play a key role in enhancing the electrochemical properties. In this work, S/N/O co-doped biocarbon with a unique lotus-root-like structure and abundant micropores was prepared by two-step pyrolysis using pine sawdust, a typical forestry waste, as the raw material, thiourea as a pore expander and dopant, which expanded the role of K₂C₂O₄·H₂O as an activator. The maximum specific surface area(SSA) of the materials is as high as 2215 m² g⁻¹, and the best sample has the largest mass specific capacitance (320.15F g⁻¹) as well as the best ultra-high microporosity (93.29 %). The assembled aqueous supercapacitor button type device possessed a coulomb efficiency of 99.97 % and capacity retention of 94.15 % after 20,000 cycles, indicating its extraordinary cycling stability. This study provides a feasible path for the resourceful treatment of forestry waste and the preparation of microporous-rich materials.