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- Title
High Polymer Content 2,5-Pyridine-Polybenzimidazole Copolymer Membranes with Improved Compressive Properties.
- Authors
Molleo, M. A.; Chen, X.; Ploehn, H. J.; Benicewicz, B. C.
- Abstract
Three series of polybenzimidazole (PBI) random copolymers (2,5-pyridine-r-meta-PBI, 2,5-pyridine-r-para-PBI, and 2,5- pyridine-r-2OH-PBI) were synthesized and cast into phosphoric acid (PA) doped membranes using the PolyPhosphoric Acid (PPA) Process. Copolymer composition was adjusted using co-monomers that impart high and low solubility characteristics to simultaneously control overall copolymer solubility and gel membrane stability. Measured under a static compressive force at 180 °C, copolymer membranes generally exhibited decreased creep compliance with increasing polymer content. Within each series of copolymer membranes, increasing polymer contents proportionally reduced the phosphoric acid/polymer repeat unit (PA/PRU) ratios and their respective proton conductivities. Some copolymer membranes exhibited comparable fuel cell performances (up to 0.66V at 0.2 Acm-2 following break-in) to para-PBI (0.68 V at 0.2Acm-2) and equal to 3,5-pyridine-based high solids membranes. Furthermore, 2,5-pyridine copolymer membranes maintained a consistent fuel cell voltage of >0.6 V at 0.2 Acm-2 for over 8600 h under steady-state operation conditions. Phosphoric acid loss was monitored during long-term studies and demonstrated acid losses as low as 5.55 ng cm-2 h-1. The high-temperature creep resistance and long-term operational stabilities of the 2,5-pyridine copolymer membranes suggest that they are excellent candidates for use in extended lifetime electrochemical applications.
- Subjects
PROTON exchange membrane fuel cells; PERFORMANCE of fuel cells; POLYPHOSPHORIC acid; STEADY-state responses; RANDOM copolymers
- Publication
Fuel Cells, 2015, Vol 15, Issue 1, p150
- ISSN
1615-6846
- Publication type
Article
- DOI
10.1002/fuce.201400129