PFSA ,

Healy, J., Hayden, C., Xie, T., Olson, K., Waldo, R., Brundage, A., Gasteiger, H. A. and Abbott, J. 2005. Aspects of the chemical degradation of PFSA ionomers used in PEM fuel cells. Fuel Cells 5 302-308. 

For instance, the Dow experimental membrane and the recently introduced Hyflon Ion E83 membrane by Solvay-Solexis are "short side chain" (SSC) fluoropolymers, which exhibit increased water uptake, significantly enhanced proton conductivity, and better stability at T > 100°C due to higher glass transition temperatures in comparison to Nafion. The membrane morphology and the basic mechanisms of proton transport are, however, similar for all PFSA ionomers mentioned. The base polymer of Nation, depicted schematically in Figure 6.3, consists of a copolymer of tetrafluoro-ethylene, forming the backbone, and randomly attached pendant side chains of perfluorinated vinyl ethers, terminated by sulfonic acid head groups. °... 

Transport properties of hydrated PFSA membranes strongly depend on nanophase-segregated morphology, water content, and state of water. In an operational fuel cell, these characteristics are indirectly determined by the humidity level of the reactant streams and Faradaic current densities generated in electrodes, as well as the transport properhes of catalyst layers, gas diffusion layers, and flow... 

Impregnating these layers with PFSA ionomer for enhanced proton conduction or hydrophobizing agents like Teflon for sufficient gas porosity is optional. However, ionomer impregnation is indispensable in CLs with thicknesses of > 1 ftm. Ultrathin CLs with - 100-200 nm, on the other hand, can operate well without these additional components, based on sufficiently high rates of transport of dissolved reactant molecules and protons in liquid water, which could ensure uniform reaction rate distributions over the entire thickness of the layer. 

SPE strategies have been carried out using a variety of media according to the different polarities exhibited by PFCs. Ionic perfluorocarboxylates (PFCAs) and perfluorosulphonates (PFSAs) require moderately polar media (Oasis WAX-SPE or methanol and acetonitrile) for efficiently trapping of water-soluble short-chain... 

The trimethylsilyl group is exchanged for a hydrogen atom using PfSA in acetonitrile, a reaction referred to as a protodesilylation Protonation of vinylsilane 7 leads in the process first to cation 25, which is stabilized by the p-effect of silicon.10 A nucleophile subsequently abstracts the TMS group, producing olefin 8. Vinylsi-lanes can be transformed into olefins not onl> with acid.10 but also with fluoride1011 or with catalytic amounts of iodine m the presence of water... 

The built-in and operation stresses are the consequences of the large swelling and shrinkage of the ionomer membrane when it uptakes and loses water. This is frequently referred to as dimensional instability in the literature. Water in the PFSA membrane is an essential ingredient of its proton conduction behavior. Water affects the morphology13,14 of the ionic clusters (at nanoscale) which... 

Early research of ionomer membrane degradation was conducted in the context of PEM electrolyzers. The detection of fluoride and other chain fragments in the condensed effluent water indicates the decomposition of PFSA ionomer and has long been noticed. Baldwin15 reported the detection of fluoride in the effluent of PEM electrolyzer and believed that it is the result of membrane mechanical failure. Extensive research has been conducted to elucidate the reaction pathways for membrane decomposition. Many controversial results and mechanisms have been reported in the literature, demonstrating the complex nature and the current inadequate understanding of the membrane degradation mechanisms. 

Mittal postulated that radical formation is likely due to the chemical reaction of H2 and 02 on Pt surface, this reaction is chemical in nature and shows strong dependence on the surface properties of Pt particles, and the sulfonic acid groups in the PFSA membrane maybe the key to the radical attack mechanisms.27 Cipollini28 in... 

Figure 14. Strain-to-failure versus number of cycles for two types of MEAs one with a reinforced composite membrane (Gore-5510) and the other with regular PFSA membrane (N- 111). The samples are cycled from 30 to 80% RH and from 80 to 120% RH.37...

From Figure 27, one can see that the Pes parameter, both for free Hg, /36s, and Hg, pfsA, acquires a strong photoelectron energy dependence near threshold. This is due to an exchange of oscillator strengths in the two relativistic channels ns epi/2 and ns zp3/2. Thus, this is a relativistic effect. 

Perfluorosulfonic acid (PFSA) - polyelectrolyte PEO polyethylene oxide), and polymer electrolyte... 

Figure 3 shows some polymer structures of other sulfonic-acid-based materials and Fig. 4 shows the conductivity of propanesulfonated polybenzimidazole, showing the strong decrease in conductivity of PFSA above 80 °C and the much more thermally stable PBI derivative. 

Perfluoroalkylsulfonic acids have the general structure F(CF2) S03H, where typically = 4, 6, 8 or 10 (Table 3.1). The most common PFSA is perfluorooctanesulfonic acid (PFOS, = 8). Given the small pAa values of these compounds, approximately—12 [1], PFSAs dissociate completely in the environment ... 

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