Nafion membranes reinforced with magnetically controlled Fe3O4–MWCNTs for PEMFCs

Abstract

A novel composite membrane consisting of Nafion proton exchange polymer and Fe₃O₄–MWCNT (multiwall carbon nanotube) nanoparticles was prepared through solution-casting. By applying a magnetic field beneath the mixture during casting, the Fe₃O₄–MWCNT particles are drawn to one side of the membrane, promoting the formation of distinct Nafion-rich and Fe₃O₄–MWCNT-rich layers in the through-thickness direction of the cured membrane. This technique provides increased mechanical reinforcement to the membrane due to the presence of MWCNTs while preserving low electrical conductivity in the through-thickness direction due to the Fe₃O₄–MWCNT-free layer created by the magnetic field. The precursor Fe₃O₄–MWCNT nanocomposite was synthesized using wet chemistry techniques. Its crystal structure, morphology, and MWCNT content were verified using X-ray diffraction, transmission electron microscopy, and thermogravimetric analysis. Composite [Fe₃O₄–MWCNT]–Nafion membranes were synthesized with and without the application of a magnetic field. Scanning electron microscopy and energy dispersive X-ray spectroscopy were applied to the membranes and used to confirm the formation of two functional layers. Their tensile strength, electrochemical impedance, and fuel cell performance were also characterized and compared with pure Nafion membranes. It is shown that the magnetic preparation technique can be used to synthesize composite Fe₃O₄–MWCNT-reinforced Nafion membranes with improved tensile strength and equivalent fuel cell performance to pure Nafion. These membranes can potentially replace pure Nafion membranes in PEMFCs because thinner membranes with equivalent strength can be produced, resulting in increased performance.