Synthesis and characterization of reduced graphene oxide/iron oxide/silicon dioxide (rGO/Fe3O4/SiO2) nanocomposite as a potential cathode catalyst

Abstract

A nanocomposite comprising reduced graphene oxide/iron oxide/silicon dioxide (rGO/Fe 3 O 4 /SiO 2 ) was synthesized through a facile one-pot method. Synthesis was initiated by reduction of graphene oxide that was later mixed with Fe 2+ and Fe 3+ ions before adding tetraethyl orthosilicate to induce SiO 2 and producing the desired electrocatalyst. Physical and electrochemical characterization were carried out using Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller analysis (BET), cyclic voltammetry, and electron impedance spectroscopy. The FTIR confirmed the presence of functional groups such as O–H, C=C, and C=O groups and the existence of a SiO 2 peak in the spectrum of rGO/Fe 3 O 4 /SiO 2 , while Raman spectroscopy displayed the vibrational bands of carbon materials studied. The XRD analysis showed the presence of rGO, Fe 3 O 4 , and SiO 2 diffraction peaks. The SEM-EDX and TEM confirmed the unification of the compound as a nanocomposite with differences in morphologic structure. The TGA demonstrated the thermal stability of the nanocomposite, while BET analysis showed that the nanocomposites fell in the mesopore region. The nanocomposite was then drop-casted on the surface of a glassy carbon electrode (GCE) for fabrication of an electrode denoted as rGO/Fe 3 O 4 /SiO 2 /GCE. Electrochemical studies showed that the current response of the modified rGO/Fe 3 O 4 /SiO 2 /GCE was greater than bare GCE in terms of rapid electron transfer and minimal resistance charge transfer. These were shown by the peak current at anode and cathode values of 101.2 and 88.4 μA, respectively, with peak potential separation of 100 mV. Meanwhile, lowest resistivity was observed for rGO/Fe 3 O 4 /SiO 2 /GCE at 54.2 Ωm 2 , decreasing almost 10-fold compared to the bare GCE. Moreover, its high apparent electron transfer rate constant of 9.71 × 10 −4 cm s −1 indicated its high electron transfer rate process. Therefore, this work supports the potential of rGO/Fe 3 O 4 /SiO 2 /GCE composite as a substitute for platinum as a cathode material. • First synthesis of reduced graphene oxide (rGO)–iron oxide–silica nanocomposite. • Adding silica to rGO–iron oxide increases its electrochemical activity. • Nanocomposite is suitable for prospective oxygen reduction electrocatalyst.