Perfluorosulfonic acid polymer water content

The internal resistance of the polymer electrolyte membrane depends on the water content of the membrane. The water ionizes add moieties providing mobile protons, like protons in water [1-3]. Absorbed water also swells the membrane, which may affect the interface between the polymer electrolyte and the electrodes. Nafion, a Teflon/perfluorosulfonic acid copolymer, is the most popular polymer electrolyte because it is chemically robust to oxidation and strongly acidic. The electrodes are commonly Pt nanoparticles supported on a nanoporous carbon support and coated onto a microporous carbon cloth or paper. These structures provide high three-phase interface between the electrolyte/catalyst/reactant gas at both the anode and cathode. 

Water Flux in Polymer Electrolyte Membranes Water flux in the solid electrolyte membrane of the PEFC must be understood to grasp the concept of a local water balance in the fuel cell. From Chapter 5, we know that the ionic conductivity of perfluorosulfonic acid-based solid polymer electrolytes is a strong function of water content. Within the electrolyte, there are four basic modes of transport, as schematically illustrated in Figure 6.21 ... 

In general, it is known that the proton conductivity does not directly correlate with either water uptake or lEC for any of the polymers applicable in fuel cell technology. Sulfonated hydrocarbon polymers usually have greater water uptake than the perfluorosulfonic polymers in order to achieve the same proton conductivity, which is probably because the acid content in the hydrocarbon polymers is much lower... 

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