PBI powder (Goodfellow) was disolved in N,N-dimethylacetamid
(DMAc) at 70 ◦C under stirring. 5 wt% PBI solution in DMAc
was poured in a glass mold and placed in a vacuum furnace at 80 ◦C
for 4 h to cast a membrane of thickness ranging from 50 m to
150 m. The resulting membrane was immersed in 68.8 wt% H3PO4
(10.64 M) for at least 72 h prior to use in order to protonate the
imidazole ring.