Membrane Electrolytes with Magnetic Field Aligned Graphene Oxide Nanosheets for Alkaline Fuel Cells

This study aims to elucidate the magnetic graphene oxide (GO) nanofiller alignment in polymer matrix on the resulting films’ ionic conduction and methanol barrier properties. Magnetic iron oxide (Fe₃O₄) nanoparticles were fabricated and decorated onto the GO nanosheets. The magnetic GO-Fe₃O₄ nanofillers were mixed with quaternized polyvinyl alcohol (QPVA) to form polymer composite. By applying magnetic field on parallel sides along in-plane direction during drying and film formation step, the GO-Fe₃O₄ nanosheets were aligned in an orientation parallel to the direction of magnetic field and connected each other into elongated domains. The QPVA composite membranes were doped with alkali to become hydroxide-conducting electrolytes for direct methanol fuel cell application. The magnetic field-aligned QPVA/GO-Fe₃O₄ membrane showed higher ionic conductivity and lower methanol permeability compared to nonaligned QPVA/GO-Fe₃O₄ membrane. The aligned QPVA/GO-Fe₃O₄ composite exhibited a peak power density of 172.4 mW cm^-2 at 60°C, 35.6% higher than that without magnetic field treatment.