(589e) Mechanical Properties of Nafion and Nafion/Titania Membranes for Pem Fuel Cells

The addition of metal oxide particles to recast Nafion membranes has been found to improve fuel cell performance, particularly at high temperatures and reduced humidity.[1] Operation under these conditions is desirable for enhanced CO tolerance and heat management, yet often causes membrane drying, reducing proton conductivity and over-all cell performance.

The specific qualities of composite membranes that lead to enhanced cell performance should be identified to further engineer improvements. Membrane mechanical and water-sorption properties are examined here and comparisons are made between Nafion and Nafion/Titania composite membranes. Special attention is paid to membrane behavior in confined spaces (as encountered in a tightly sealed fuel cell) in which dimensional swelling and water uptake might be inhibited.[2] Nafion/Titania composite membranes are found to have a slightly higher swelling pressure, consistent with a slightly higher Young's modulus. The interplay of thermodynamics and kinetics in Nafion water sorption?sulfonic acid solvation, concentration-driven and concentration-dependent diffusion, elastic chain stretching and viscoelastic chain relaxation and rearrangement--will be examined in light of measured mechanical properties of the membrane.

1. Yang, C., et al., A comparison of physical properties and fuel cell performance of Nafion and zirconium phosphate/Nafion composite membranes. Journal of Membrane Science, 2004. 237(1-2): p. 145-161.

2. Satterfield, M.B., et al., Mechanical Properties of Nafion and Titania/Nafion Composite Membranes for PEM Fuel Cells. J. Polymer Science B: Polymer Physics, 2006. In Press.