Wasted rose-derived porous carbons with unique hierarchical heteroatom-enriched structures as a high-performance supercapacitor electrode†

High-quality and low-cost activated carbons (ACs) are highly considered as high-performance electrode materials for next-generation supercapacitors. Herein, self-heteroatom-doped nanoporous activated carbon (AC) powders were prepared from wasted rose flowers via two different activation approaches, namely, a typical acidic approach with H₃PO₄ (AC-T) and a green self-activation approach (AC-S). Based on morphological characterizations, the typical activation method resulted in ACs with a surface area of 1124 m² g⁻¹, while the ACs prepared by the AC-S method retained the initial hierarchical porous rose structure with a higher surface area of 1556 m² g⁻¹. High-resolution transmission electron microscopy (HRTEM) images revealed extensive graphitized regions in the porous microstructure of the AC-S powders. Electrochemical analysis results demonstrated an outstanding gravimetric capacitance of 539 F g⁻¹ at 1 A g⁻¹ for AC-S in a three-electrode system. In addition, the prepared electrode with AC-S exhibited excellent stability with 95.4% capacitance retention after 6000 cycles. The symmetric supercapacitor device based on this sample also exhibited a high gravimetric capacitance up to 365 F g⁻¹ and an ultra-high energy density of 50.7 W h kg⁻¹ at a power density of 500 W kg⁻¹.