Preparation of rGO-wrapped magnetite nanocomposites and their energy storage properties

Abstract

Porous reduced graphene oxide (rGO)/Fe₃O₄ nanocomposites have been prepared in this study by a simple precipitation reaction followed by freeze drying. When the sample was dried at 80 °C, spinel phase of Fe₃O₄ wrapped by rGO sheets was obtained without any detectable impurities. It exhibits a high surface area of 30 m² g⁻¹. The rGO/Fe₃O₄ composites were also annealed under different conditions such as 600 °C in Ar, 700 °C in Ar and 700 °C in Ar–H₂ to understand the effect of annealing temperature on the electrochemical properties. The rGO content in the samples was found to be ∼3–4% in all the composites from CHNS analysis. Electrochemical properties of the different composites were investigated by cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy studies. The composite prepared at 80 °C exhibits very high capacity of 1254 mA h g⁻¹ for the first charge cycle. However, the capacity faded to 1046 mA h g⁻¹ at the end of 40 cycles. Though the high temperature annealed samples show slightly decreased capacity, they show excellent capacity retention with good rate capability. The rGO/Fe₃O₄ composite obtained at 700 °C in Ar–H₂ exhibits high reversible capacity of 480 mA h g⁻¹ at a high current density of 3000 mA g⁻¹.