Meta-PBI/methylated PBI-OO blend membranes for acid doped HT PEMFC

Hyeongrae Cho, Eun Hur, Dirk Henkensmeier, Gisu Jeong, Eunae Cho, Hyoung Juhn Kim, Jong Hyun Jang, Kwan Young Lee, Hans Aage Hjuler, Qingfeng Li, Jens Oluf Jensen, Lars Nielausen Cleemann

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Abstract

Methylation of polybenzimidazole leads to positively charged polymer backbones, and moveable anions. Ion exchange of methylated PBI-OO in phosphoric acid (PA) shows that the resulting polymers dissolve. meta-PBI, however, absorbs about 400 wt% PA while remaining a self supported membrane. We investigate the properties of blend membranes, employing meta-PBI for mechanical integrity and methylated PBI-OO for high PA uptake and resulting proton conductivity. While small additions of PBI-OO decrease the tensile strength of blend membranes (58 MPa for 10% PBI-OO), further addition leads to an increase, and 50% blend membranes show again a tensile strength of 74 MPa, just 3 MPa lower than pure meta-PBI membranes. Thermal stability of iodide exchanged blend membranes appears to be remarkably high, probably because cleaved iodomethane does not evaporate but methylates meta-PBI. PA concentration in doped membranes of 60-63% is reached by doping in 60% PA (blend; 6.3 PA/repeat unit) and 70% PA (meta-PBI; 4.6 PA/r.u.). This suggests that blends absorb PA more strongly. Both membranes show similar conductivity between rt and 140 °C, indicating that PA concentration describes these membranes better than PA/r.u. In the fuel cell, blend membranes show similar or better performance than meta-PBI. In the TGA, blends doped in 20% PA showed a stable plateau between 115 and 180 °C, while meta-PBI lost weight continuously.

Original languageEnglish
Pages (from-to)135-143
Number of pages9
JournalEuropean Polymer Journal
Volume58
DOIs
Publication statusPublished - 2014 Jan 1

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ASJC Scopus subject areas

  • Polymers and Plastics
  • Physics and Astronomy(all)
  • Organic Chemistry

Cite this

Cho, H., Hur, E., Henkensmeier, D., Jeong, G., Cho, E., Kim, H. J., Jang, J. H., Lee, K. Y., Hjuler, H. A., Li, Q., Jensen, J. O., & Cleemann, L. N. (2014). Meta-PBI/methylated PBI-OO blend membranes for acid doped HT PEMFC. European Polymer Journal, 58, 135-143. https://doi.org/10.1016/j.eurpolymj.2014.06.019