Self-doped porous carbon derived from traditional Chinese medicine residues for high performance supercapacitors

To achieve high-value utilization of herbal residues, this study employed rhubarb residue - representative of mixed herbal residues' composition - to prepare porous carbon for supercapacitor applications. By controlling the preparation process, the inherent heteroatoms from the raw material were effectively retained, achieving self-doping of nitrogen and oxygen. As-synthesized porous carbon exhibits an ultrahigh specific surface area of 2817 m2/g with well-defined hierarchical porosity. This structural architecture provides abundant active sites for charge storage while facilitating rapid ion diffusion. Furthermore, the presence of self-doped nitrogen (2.07 at%) and oxygen (9.76 at%) enhances the specific capacitance through pseudocapacitive contributions. When employed as supercapacitor electrodes, the materials deliver a remarkable electrochemical capacitance of 356 F/g at 1 A/g and maintain superior rate capability, retaining 274 F/g at 10 A/g. The electrodes also exhibit exceptional cycling stability, with 93.5 % capacitance retention after 10,000 cycles at 10 A/g. These findings innovatively demonstrate that employing lower temperatures and shorter activation times can effectively retain heteroatoms in Chinese herbal residues. This not only confirms the suitability of herbal residues as premium raw material for capacitor carbon production but also provides a viable strategy for high-value utilization of biomass waste in supercapacitor applications.