Magnetic field-assisted alignment of graphene oxide nanosheets in a polymer matrix to enhance ionic conduction

This study aims to elucidate the effect of magnetic graphene oxide (GO) alignment in a polymer matrix on the ionic conduction and methanol barrier properties of the resulting composites. Magnetic iron oxide (Fe₃O₄) nanoparticles were fabricated and anchored on GO nanosheets. The magnetic GO-Fe₃O₄ nanofillers were incorporated into a quaternized polyvinyl alcohol (QPVA) matrix to form a polymeric composite. By applying a magnetic field (MF) along the in-plane direction during the drying and film formation steps, the GO-Fe₃O₄ nanosheets were aligned in an orientation parallel to the direction of the MF and connected to each other in elongated domains, as confirmed using transmission electron microscopy, field emission scanning electron microscopy/energy dispersive X-ray spectroscopy mapping, and laser scanning microscopy. The MF-aligned QPVA/GO-Fe₃O₄ electrolyte possessed higher conductivity and lower permeability than the un-aligned QPVA/GO-Fe₃O₄ membrane and pristine QPVA film. The aligned QPVA/GO-Fe₃O₄ composite exhibited a peak power density of 172.4 mW cm⁻² at 60 °C, which is higher than those of the composite without the MF treatment (67.7 mW cm⁻²) and the pristine QPVA (50.3 mW cm⁻²). This research demonstrates the extraordinary benefits of MF assisted GO-Fe₃O₄ nanofillers in facilitating the ion conduction and barrier property of a polymeric composite at 0.1% filler loading.