Enhancing Adsorption and Electronic Properties by Incorporating Layered Bismuthene into Sustainable Heteroatom‐Doped Carbon Spheres for High Energy Density Supercapacitors

In this work, a novel nanocomposite (NC) was fabricated by ultrasonically self-assembling bismuthene(Biene) nanosheets with nitrogen and sulfur-doped carbon spheres (NSCS) derivedfrom Artocarpus heterophyllus peel waste. Structural and morphological analysesconfirmed the successful integration of Biene into the NSCS matrix, forming ahierarchical architecture with a high specific surface area (1994 m² g^-1) anduniform elemental dispersion. Density functional theory (DFT) calculationsrevealed a substantial bandgap reduction from 0.95 to 0.071 eV, strong orbitalhybridization near the Fermi level, and favorable potassium (K) adsorptionenergy (-0.973 eV), indicating efficient charge transfer and enhancedelectronic conductivity. Electrochemical measurements demonstrated a highspecific capacitance of 855.8 F g^-1 at 10 mV s^-1 and 665 F g^-1 at 1 A g^-1, along with a low charge transferresistance (6.74 Ω).Capacitance contribution analysis using power law, Trasatti, and Dunn methodsshowed predominant surface-controlled behavior (87.4%) and adiffusion-controlled contribution (12.6%) with a b-value of 0.54. TheNSCS/Biene-based symmetric supercapacitor device operated at 2.0 V, deliveringa high energy density of 40.3 Wh kg^-1 and a power density of 10 000 W kg^-1, with excellent cycling stability (86.2% retention)and coulombic efficiency (97.7%) over 10 000 cycles, indicating its strongpotential for next-generation energy storage systems.