| Summary: | Conducting fillers based on 2-hydromethyl) trimethylammoniun dimethyl phosphate (IL1), N,N-dimethyl-N-(2-hydroxyethyl) ammonium bis(trifluoromethanesulfonyl)imide (IL2) and 1-H-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (IL3) encapsulated in large pore zeolites (NH4BEA and NaY) have been added to the PBI casting solution for the preparation of high temperature proton exchange membranes (HTPEMs). The filler loading has been systematically varied from 3% to 20% wt. for all the studied composites. The morphological, physicochemical, and electrochemical properties of the as prepared hybrid doped PBI membranes have been fully characterized. For a given conduction filler, the optimum loading is found to be 3% wt. as inferred from the conductivity measurements at 0.05 water molar fraction. Among the tested, the outstanding electrolyte membranes are those containing IL3-NaY. The exhibited through-plane proton conductivity is 54 mS cm-1 at 200 °C for the optimum PBI + IL3-NaY_3%wt hybrid membrane. The so obtained results are explained by the assisted 1-H-3-methylimidazolium and bis(trifluoromethanesulfonyl)imide hydrogen bonding type interactions, clearly beneficial for the proton conduction processes. Moreover, the H2 permeability values for the hybrid electrolyte membranes and pure PBI are quite similar at the examined conditions; indicating the suitability of the preparation procedure in terms of fuel cross-over. The H+/H2 transport selectivity of the optimum IL3-NaY composite membrane clearly outperforms pure PBI and zeolite-PBI counterparts at 50°, 100° and 150 °C. Finally, the optimum composite membranes have been validated in H2/O2 single cell under non humidified conditions up to 180 °C as a “proof of concept” demonstration.
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