The synthesis and super capacitive characterization of microwave-assisted highly crystalline α-Fe2O3/Fe3O4 nanoheterostructures

Abstract

A facile microwave-assisted solvothermal process for the synthesis of narrow-size distributed α-Fe₂O₃, α-Fe₂O₃/Fe₃O₄, and Fe₃O₄ nanostructures was demonstrated using PVP as a surfactant. During the reaction, the influence of the reaction media, such as the mixture of ethylene glycol and water on the formation of α-Fe₂O₃, α-Fe₂O₃/Fe₃O₄, and Fe₃O₄ was systematically studied. Interestingly, pure aqueous medicated solvothermal reaction conferred phase pure rhombohedral Fe₂O₃ (hematite) and linearly upsurging the formation of cubic Fe₃O₄ (magnetite) with the increasing concentration of EG and further, in pure EG, it deliberated cubic Fe₃O₄. FESEM and FETEM images of α-Fe₂O₃/Fe₃O₄ nano heterostructure clearly showed the nanosized Fe₃O₄ particles of 4–6 nm decorated onto Fe₂O₃ nanoparticles. Further, the electrochemical properties of α-Fe₂O₃, α-Fe₂O₃/Fe₃O₄, and Fe₃O₄ nanoparticles were investigated with galvanostatic charge–discharge and cyclic voltammetry measurements using a 3-electrode system. The findings show that their specific capacitances are linked to the type of iron oxide. More significantly, the α-Fe₂O₃/Fe₃O₄ nanoheterostructure exhibited the utmost capacitance of 165 F g⁻¹, which is greater than that of pristine α-Fe₂O₃ and Fe₃O₄. Enhancement in the electrochemical performance was found due to the improved charge transfer that occurred at the interface of the nanoheterostructure. The nanoparticles of Fe₃O₄ deposited on the Fe₂O₃ increased the active sites, which accelerated the process of adsorption and desorption of ions, thereby enhancing the interface-assisted charge transfer and reducing the internal resistance, which is ultimately responsible for enhanced capacitance. Such heterostructures of nano iron oxide may fulfill the requirements of electrodes in supercapacitors.