Phosphoric-acid-doped polybenzimidazole structures

Current research activities are focused on the identification of membrane materials and structures with high proton conductivity and low methanol permeability. Ultimately, one would tike membranes that work well in a DMFC at 10-20 M methanol, but the focus of most research is on much lower methanol feed concentrations (0.5 and 1.0 M). Since DMFCs are designed primarily for the portable power/electronics market, operating temperatures in the 25-80°C range are usually considered. Extensive data is available in the literature on new membrane materials with reduced methanol permeability, including sulfonated or phosphonated copolymers, phosphoric-acid-doped polybenzimidazole, and various blends and composites (see Table 29.6 for a listing of DMFC properties). 

Figure 10.8 Chemical structure of (a) polybenzimidazole (PBI) and (b) phosphoric acid-doped PBI.

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