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

Abstract 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 m ² 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.