Surfactant-assisted hydrothermal synthesis of NiFe2O4/reduced graphene oxide composites

Abstract

The effect of the presence of cetyltrimethylammonium bromide (CTAB) on the structural, magnetic, morphological, and electrophysical properties of NiFe2O4/reduced graphene oxide composite materials has been studied. The synthesized materials have been characterized by powder X-ray diffraction (XRD), Mössbauer and impedance spectroscopy, powder, scanning electron microscopy (SEM), N2 adsorption–desorption isotherm measurement and TEM techniques. It has been found that the presence of CTAB makes it possible to obtain mesoporous composites with the presence of micropores, high specific surface area, and good conductivity. A thermal treatment stage at temperature > 300 °C in an argon atmosphere is a mandatory stage to remove CTAD residues and increase the BET specific surface area (up to 221 m2/g). The average particle sizes of the samples (calculated by Scherrer equation) of the NiFe2O4/rGO composite have shown a low dependence on the presence of CTAB (8.0–8.5 nm), but CTAB prevents particle agglomeration and promotes the formation of conduction channels. Frequency-sensitive polaron transport is the main mechanism of electrical conductivity of CTAB-assisted synthesized pure NiFe2O4 (activation energies in the range of 0.26–0.37 eV). The rGO component determines the charge transport in the NiFe2O4/rGO composite with two charge transport mechanisms – proton trapping and electron transfer between rGO particles.