Abstract:

Multi-functional FeCo nanoparticles (NPs) exhibit unique structural, magnetic, and catalytic properties, making them versatile materials with potential applications in diverse fields. In this work, we investigated the structural, electrochemical, and magnetic properties of as- prepared FeCo NPs synthesis by polyol method. X-ray diffraction analysis revealed multiphase structures: FeCo and α-Fe2O3 phases and scanning electron microscopy images confirmed spherical-like structures of FeCo NPs with an average size of 12.4 ± 0.1 nm. The electrochemical properties of FeCo NPs were investigated using a three-electrode setup in a 1 M KOH electrolyte at room temperature. The onset potentials for FeCo catalysts were found to be -0.15 V for ORR, 0.25 V for OER, and -1.26 V for HER. Tafel measurements further elucidated the reaction mechanism, revealing corrosion potentials of -0.165 V for ORR and 0.215 V for OER, with Tafel slopes of 228 mV dec-1 and 48 mV dec-1, respectively. A significant increase in magnetization was observed below 25 K in both zero-field-cooled and field-cooled curves, a magnetic transition temperature, Ts, occurs at 15 K, possibly indicating a ferromagnetic-to-antiferromagnetic phase transition. The hysteresis loop measurements revealed coercive field values ranging from 968 Oe at 5 K to approximately 206 Oe at 320 K, indicating a relaxation in magnetic spin orientation with increasing temperature. The saturation magnetization (Ms) values were recorded as 15.2 emu/g under a 5 T magnetic field, and the remanent magnetization (Mr) showed dominant ferromagnetic properties at 5 K with an Mr/Ms ratio indicating soft magnetic behavior. The magnetic susceptibility of FeCo NP exhibited a peak at approximately 25 K, and the Curie-Weiss law provided an estimated θ angle of -9.58°, suggesting antiferromagnetic interactions.

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