Fabrication of oxygen-rich/nitrogen-doped hierarchical porous Ganoderma lucidum spore activated carbon for enhanced supercapacitor performance

Hierarchical porous carbon-based biomass is considered the most promising functional carbon-based electrode material for energy conversion and storage as a result of its abundant natural resources, multi-heteroatom self-doping and easy of modification. In this study, Ganoderma lucidum spore-derived carbon material (GLSC–2) with oxygen-rich/nitrogen-doped three-dimensional, hierarchically connected porous structure was synthesized by a two-step route of pre-oxidation in air followed by KOH etching. It is worth noting that pre-oxidation in air can not only preserve the natural cage-like structure of spores, but also introduce a significant number of oxygen-containing functional groups with the help of atmospheric oxygen. The synthesized GLSC–2 possessed high O content (14.27%), moderate N content (1.99%) and relatively high specific surface area (1524.73 m² g⁻¹), along with high-density micropores and narrow mesopore distribution, which were crucial for promoting rapid ion diffusion and improving the electrochemical performance of supercapacitors. Encouragingly, GLSC–2 exhibited an attractive specific capacitance of 261.13 F g⁻¹ at 1 A g⁻¹ and excellent rate capability. Even at a high current density of 10 A g⁻¹, the capacitance retention rate remained at 81.60%. After 10,000 cycles of charge–discharge at 2 A g⁻¹, the capacity retention rate and Coulombic efficiency were maintained at 98.63% and 99.19%, respectively. When assembled into a symmetric supercapacitor (GLSC–2//GLSC–2), the energy density reached 9.03 Wh kg⁻¹, with a power density approaching 500 W kg⁻¹. This study provides a more economical and convenient route for the production of high-performance oxygen-rich/nitrogen-doped electrode materials based on renewable biomass.