Methanol permeability performance data

Table 5.1 Summary of membrane proton conductivity and methanol permeability performance data.

While promising results were reported with all of the above systems, especially encouraging direct methanol fuel-cell performance data were obtained with membrane prepared from blends of sulfonated poly[bis(phenoxy)phos-phazene] (SPBPP) and PBI [34]. The effect of FBI content on room-temperature membrane proton conductivity, room-temperature water uptake, and methanol permeability (at 60°) is shown in Fig. 12. 

High proton conductivity and low methanol permeability (PCH3OH) are two of the essential characteristics that a polymer electrolyte membrane should possess to constitute a viable alternative to Nafion in DMFC applications. These parameters may be combined to constitute the p selectivity (or, shortly, selectivity p = log[ff/P]), which is useful for clearly comparing various sPEEK membranes. Indeed, p selectivity is a common metric for evaluating membrane performances and, as reported in Table 3.6, the few data about p selectivity show that the selectivity decreases with increasing DS. Indeed, as stated earlier, for DS >70%, sPEEK becomes more soluble in methanol and, as a consequence, methanol permeability increases determining a depletion of p selectivity. 

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