Proton-conducting membranes based on poly(2,5-benzimidazole) (ABPBI) and phosphoric acid prepared by direct acid casting

摘要

We report the preparation of phosphoric acid doped poly(2,5-benzimidazole) (ABPBI) membranes for PEMFC by simultaneously dopingudand casting from a poly(2,5-benzimidazole)/phosphoric acid/methanesulfonic acid (MSA) solution. The evaporation of MSA yields a veryudhomogeneous membrane having a better controlled composition, avoiding the use of solvent-intensive procedures. Membranes have beenudprepared with contents of up to 3.0H3PO4 molecules per ABPBI repeating unit. These membranes achieve a maximum conductivity of 1.5ud ~ 10.2 S cm.1 at temperatures as high as 180 .C in dry conditions. These ABPBI membranes are more conveniently prepared than thoseudconventionally formed and doped in separate steps while featuring comparable conductivities (ABPBI ~ 2.7H3PO4 prepared by the soakingudmethod showed a conductivity of 2.5 ~ 10.2 S cm.1 at 180 .C in dry conditions).