Magnetic iron oxide (Fe3O4)/carbon nanostructures as cost-effective bifunctional electrodes for energy storage (supercapacitors) and water splitting (OER)

Abstract

The development of low-cost, durable, and multifunctional materials for energy storage and conversion is crucial for sustainable energy technologies. This study involved the synthesis of magnetite (Fe₃O₄) nanoparticles and their composites with carbon nanomaterials: graphite (G), carbon fibers (CF), and carbon nanotubes (CNTs), using a straightforward one-pot co-precipitation process facilitated by ultrasonic irradiation. The electrochemical performance was assessed for supercapacitor and oxygen evolution reaction (OER) applications in an alkaline electrolyte. Among the examined materials, Fe₃O₄@CF exhibited the highest specific capacitance of 106 F/g at 1 A/g, with exceptional stability, maintaining 100% efficiency after 5000 cycles. The composites exhibited hybrid charge-storage characteristics, arising from electric double-layer capacitance (EDLC) and Fe²⁺/Fe³⁺ pseudocapacitance. Moreover, Fe₃O₄ and its composites demonstrated commendable OER activity with low overpotentials of 360–400 mV. The results indicate that Fe₃O₄–carbon nanocomposites, produced using a simple method, are potential bifunctional materials for energy storage and water oxidation applications.