Biomass-Derived Mesoporous Carbon from Royal Poinciana Flowers: A Unique Approach for Pseudocapacitive Energy Storage

This study presents the design and development of in situ nitrogen-doped mesoporous carbon with oxygen-containing functional groups, which synthesizes from royal poinciana (RP) flowers using a green and sustainable approach. The naturally occurring nitrogen in biomass serves as a heteroatom dopant, imparting redox activity to the carbon material. Comprehensive characterization techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, field emission transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy, confirm the microstructural and chemical features of the synthesized carbon. Unlike conventional biomass-derived carbons that primarily exhibit electrical double-layer capacitance, however, more significantly, the RP-derived carbon demonstrates pseudocapacitive behavior and facilitates charge storage through fast and reversible Faradaic redox reactions. A high specific capacitance of 834 F g⁻¹ at 1 A g⁻¹ was achieved, along with excellent cycling stability (80% retention after 10 000 cycles). The device also exhibited superior rate capability and delivered an energy density of 18.83 Wh kg⁻¹ and a power density of 1000 W kg⁻¹, maintaining 90% stability after 5000 cycles at 5 A g⁻¹. The enhanced electrochemical performance is attributed to the synergistic effects of oxygen and nitrogen functional groups, turbostratic structure, and mesoporosity, which improve electrical conductivity, ion adsorption, and surface redox reactions.