Sustainable AgFeO 2 –carbon nanohybrids derived from agricultural waste for high-performance supercapacitors in alkaline environments and multifunctional biomedicine

Energy is a basic need in today's world, and there is a demand for renewable energy storage technologies. Supercapacitors (SCs) are a well-known type of storage device that can meet these needs. Delafossite minerals (ABO2) have garnered much attention lately as potential materials in electrochemical energy storage technologies. In this study, sustainable AgFeO2 hybrid nanocomposites integrated into biomass-derived carbon substrates were synthesized via co-precipitation and hydrothermal techniques for dual-function energy storage and biomedical applications. Structural analysis using X-Ray Diffraction (XRD) confirmed the preservation of the delafossite AgFeO2 phase, exhibiting crystallite sizes of 6.51 nm for AgFeO2-CNT and 7.43 nm for AgFeO2-AC. Morphology studies via Scanning Electron Microscopy (SEM) revealed AgFeO2 nanoparticles anchored onto granule-like CNT frameworks, creating textured hierarchical surfaces that significantly enhance charge transmission. Fourier transform infrared (FT-IR) spectroscopy analysis verified composite formation as indicated through characteristic bands at 3280 cm-1 (hydroxyl/amine), 1563 cm-1 (CC sp2), and 515/457 cm-1 (Ag-O/Fe-O). Furthermore, X-ray Photoelectron Spectroscopy (XPS) revealed the presence of a mixture of Fe(II)/Fe(III) states and Ag-O/Fe-O coordination, indicating an abundance of active surface redox sites. Magnetic studies using a Vibrating Sample Magnetometer (VSM) demonstrated weak ferromagnetism (Ms = 2.34 × 10-3 emu g-1) suitable for magnetic separation. In electrochemical evaluations using 2 M KOH electrolyte, an AgFeO2-CNT electrode delivered a superior specific capacitance value of 970.8 F g-1 at 8 A g-1 outperforming the AgFeO2-AC electrode (935.3 F g-1) at the same current densities. The incorporation of CNTs into the AgFeO2 lattice resulted in a larger CV integrated area and lower internal resistance, indicating superior electrochemical capacitance and faster ion-diffusion rates. Long-term stability tests revealed 82.75% capacitance retention for the AgFeO2-CNT electrode after 6000 cycles. A fabricated asymmetric device exhibited high operational stability (52.90% retention over 5000 cycles) and excellent coulombic efficiency. Superior to the AgFeO2-AC system, the AgFeO2-CNT hybrid achieved a remarkable energy density of 109.21 Wh kg-1 while maintaining a power density of 3599.67 W kg-1, validating its efficacy as a sustainable and high-rate electrode material for advanced energy applications.