Construction of Novel Proton Transport Channels by Triphosphonic Acid Proton Conductor-Doped Crosslinked mPBI-Based High-Temperature and Low-Humidity Proton Exchange Membranes

High proton conductivity and sufficient stability of the polybenzimidazole membrane are important for the application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). A series of composite membranes based on crosslinked mPBI (cPBI) with cerium 2,4,6- triphosphono-1,3,5-triazine (CeTPT) were resoundingly fabricated. Novel cPBI networks with tetrafunctional N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl-methane (TGDDM) were synthesized. It is noteworthy that a new high-temperature proton conductor CeTPT was added. CeTPT contained three phosphonic acid groups, which offered good proton conductivity at moderate-to-low humidity and had good thermal stability. Tetrafunctional crosslinker TGDDM had multiple functional groups. With a relatively low crosslinking degree (CLD), the mechanical properties, dimensional stability, and oxidative resistance of the membranes were efficiently improved. The low CLD and good physicochemical stability also allowed high doping levels of CeTPT (up to 50%) and consequently high proton conductivity. At 180 degrees C and 50% RH, the proton conductivity of cPBI-5-CeTPT-50 and cPBI-10-CeTPT-50 was 0.072 and 0.068 S cm(-1), respectively. The cPBI-CeTPT membranes showed good methanol resistance and membrane selectivity, and thus the membranes were suitable for direct methanol fuel cells.

Automated summary

A series of composite membranes based on crosslinked mPBI with cerium 2,4,6-triphosphono-1,3,5-triazine (CeTPT) were successfully fabricated, showing good proton conductivity and thermal stability. The addition of new high-temperature proton conductor CeTPT, along with tetrafunctional crosslinker TGDDM, efficiently improved the mechanical properties, dimensional stability, and oxidative resistance of the membranes. These membranes exhibited high proton conductivity and good methanol resistance, making them suitable for direct methanol fuel cells.