Magnetite (Fe3O4) nanoparticles: Synthesis, characterization and electrochemical properties

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This work reports the synthesis, characterization, and electrochemical properties of magnetite nanoparticles (MNPs). MNPs were prepared by a simple solvothermal method at 200 °C for 8 h using three different concentrations of poly(vinyl)pyrrolidone (PVP). Transmission electron microscopy (TEM) images of the prepared samples reveal agglomerated like-sphere shape with mean particle sizes of ∼ 50–90 nm. The X-ray diffraction (XRD) and selected area electron diffraction (SAED) from TEM confirm the formation of pure phase Fe3O4 nanoparticles. The existence of PVP on the surface of the prepared samples is confirmed by high resolution X-ray photoemission spectroscopy (XPS). Consequently, the electrochemical performances of MNPs prepared using different PVP concentrations were evaluated by using the three-electrode cell system within 6.0M KOH. The results show that the specific capacitances was determined to be 396, 344, and 327 F/g at a scan rate of 2 mV/s and 197, 95, and 75 F/g at a current density of 3.0 A/g for MNPs samples prepared using 0.5 g, 1.0 g, and, 1.5 g of PVP, respectively. MNPs electrode showed the high power density of 777.65 W/kg with 7.36 Wh/kg of energy density addressing in high power density SC region. The cycle stability after 1000 cycles was also tested at 3 A/g and demonstrated the improvement of stability as increasing the amount of PVP. This indicates that the addition of surface element polymer plays a role in the cycle stability of supercapacitor devices.