Ultrasonic-assisted synthesis of amorphous Fe3O4 with a high specific surface area and improved capacitance for supercapacitor

Here, we provide a facile ultrasonic synthesis of amorphous Fe3O4 nanoparticles with diameters of about 5 nm using FeCl3 and the organic solvent of ethanolamine (ETA) at room condition. The intermediate of the ETA–Fe(II) complex produces Fe3O4 after hydrolysis treatment. The moderate reduction of ETA and ultrasound play an important role in the synthesis of superfine Fe3O4 particles with a very high specific surface area (270.94 m2 g− 1). The Fe3O4 nanoparticles were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), high-resolution transmission electron microscopy (HRTEM), and ultraviolet–visible absorption spectroscopy (UV–vis). Fe3O4 as an electrode material was fabricated into supercapacitor and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge measurements. The as-synthesized Fe3O4 exhibits remarkable pseudocapacitive activities including high specific capacitance (335.5 F g −1 at 0.4 A g −1), good rate capability (54.7 F g −1 at 10 A g −1), and excellent cycling stability. The novel synthetic route of Fe3O4 is a convenient and potential way for the secondary energy material which is expected to be applicable in the synthesis of other metal oxide nanoparticles.