Nafion Membranes Reinforced with Ceria-Coated Multiwall Carbon Nanotubes for Improved Mechanical and Chemical Durability in Polymer Electrolyte Membrane Fuel Cells

A composite membrane consisting of a Nafion proton exchange ionomer and ceria-coated multiwall carbon nanotubes (MWCNTs) was prepared by a solution-casting method. Reinforcement due to the presence of MWCNTs provides increased mechanical strength to the membrane, and the addition of ceria improves the membranes chemical durability by scavenging free radicals. The ceria coating also insulates the MWCNTs, which helps to preserve the membranes low electrical conductivity in the through-thickness direction. The morphology and loading of the CeO2/MWCNT precursor were verified using transmission electron microscopy and thermogravimetric analysis. The mechanical and chemical durability of the synthesized composite [CeO2/MWCNT]/Nafion membranes was compared with that of pure Nafion membranes. Composite membranes demonstrated improved tensile strength and dimensional stability during hydration, without significantly affecting electronic or ionic conductivity, and maintain equivalent polarization performance in a fuel cell system. They also showed increased durability in an open-circuit-voltage-hold fuel cell test. Such material property enhancements can extend the membrane lifetime, which increasing the economic viability of fuel cell technology.