The role of a metal ion within Nafion upon its physical and gas transport properties

• Nafion-1035 films were complexed with the following ions: Na +, Li+, K+, and Ca2+.
• Thermal stability temperature increased with metal ion type versus Nafion-H+.
• Tg and reduction relaxation behavior was greatest for Nafion-Ca2+.
• WAXD revealed no inter-chain changes within Nafion based upon ion size or valence.
• P, D, S, EP, ED, and HS were reduced with metal-ion, but not systematically.

The physical and transport properties of Li+, Na+, K+, and Ca2+ neutralized Nafion were compared to its acid form. Nafion crystallinity was disrupted with a variety of cations while average d-spacing remained constant. Higher thermal stability in metal ion exchanged Nafion was observed using TGA. Ionic interactions were probed by DMA and spectroscopic techniques. Divalent Ca2+ exhibited a distinctive influence on the chain’s mobility as compared to monovalent ions. The interaction strength cation exchanged Nafion decreased in the following order: Li+ > Ca2+ > Na+ > K+. Gas permeability increases were primarily attributed to gas solubility. Nafion had a higher gas activation energy Ep, but its permeability was lower than unsulfonated PTFE.

Figure optionsDownload as PowerPoint slide