Construction of a novel Fe₂O₃-loaded g-C₃N₄ electrodes for high-energy and sustainable asymmetric hybrid supercapacitors

Rising global energy consumption and environmental sustainability requirements demand urgent innovations in electrochemical storage. Supercapacitors, valued for rapid charge delivery and exceptional longevity, represent critical enabling technology. This study pioneers a Fe₂O₃/g-C₃N₄ (FegC) composite fabricated via ultrasonic-assisted wet impregnation, merging the faradaic reactivity of iron oxide with the conductive, nitrogen-enriched matrix of graphitic carbon nitride. Fe₂O₃ nanoparticles were prepared hydrothermally from ferric nitrate, while g-C₃N₄ sheets originated from thermal decomposition of melamine. Material characterization verified homogeneous integration, establishing an interconnected heterostructure. Electrochemical assessment yielded an unprecedented specific capacitance of 1234.54 F g⁻¹ at 1 A g⁻¹, reflecting optimized interfacial electron transport and dual charge storage mechanisms. A hybrid device configuration attained 84.22 Wh kg⁻¹ energy density at 800 W kg⁻¹, preserving 31.77 Wh kg⁻¹ under high-power conditions (8000 W kg⁻¹). The assembly exhibited ultra-long cycling stability, sustaining 84.05 % initial capacitance with 92.28 % Coulombic efficiency across 20,000 cycles, exceeding most binary metal oxide-carbon benchmarks. This performance underscores the advantage of electronic structure modulation via FegC junction formation. The work delivers a reproducible fabrication route for high-energy-density electrodes, directly supporting scalable development of sustainable power systems.