H3PO4-doped polybenzimidazole

In a cost comparison by Gebert et al. [42], it is concluded that sulfonated Polyether ether ketone (S-PEEK) and phosphoric acid-doped polybenzimidazole (H3PO4-PBI) could be a factor of five cheaper than Nafion. As discussed earlier, this cost advantage is only helpful when not offset by lower MEA power density. 

Lobato J, Canizares P, Rodrigo MA et al (2007) Improved polybenzimidazole films for H3PO4-doped PBI-based high temperature PEMFC. J Membr Sci 306 47-55... 

Fig. 7.14 Temperature dependence of proton conductivity of a 2,5-PPBI membrane with 20.4 mol H3PO4 doping. Reprinted with permission from Ref. [54] L. Xiao, et al.. Synthesis and characterization of pyridine-based polybenzimidazole for high temperature polymer electrolyte membrane fuel cell application. Fuel Cell, 5, 287-295 (2005). Copyright Wiley-VCH...

As shown in Fig. 14, PIM-1 and PIM-7 have been found to exhibit substantially higher O /Nj selectivities (a(O2/N2)>3.0) than other polymers of similar permeability [41]. Other thermally rearranged [78] polyimides show excellent CO /CH separation selectivities. These materials were also shown to function as fuel cell membranes when doped with H3PO4 and proton conductivities of 0.15 S cm" were observed at 130°C [78] that is, higher than polybenzimidazole membranes. 

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