August 1, 2012.
Fuel cells are clean and efficient energy conversion devices. The fuel cells of interest contain polymer electrolyte membranes (PEMs) that inhibit the conduction of electrons and facilitate the transport of protons. Nafion® is the most widely used membrane for fuel cell applications. However, alternatives are desired because Nafion is expensive, allows significant amounts of methanol crossover, and functions poorly at low humidity or high temperature. An acid-base blend membrane composed of both acidic sulfonated poly(ether ether ketone ketone) (Ph-SPEEKK) and basic polysulfone tethered with 5-amino-benzotriazole (PSf-BTraz) has been show to perform better than traditional acidic PEMs such as Nafion and Ph-SPEEKK. We use molecular dynamics to study the PEM morphology and the transport of water, hydronium, and methanol in Ph-SPEEKK/PSf-BTraz blend membranes. Our aim is to understand the fundamental science behind the enhanced properties of the blend membrane. Initial analysis shows that transport is slower and sulfonate groups are farther apart compared to plain Ph-SPEEKK. The decrease in methanol crossover may account for the enhanced performance Ph-SPEEKK/Psf-BTraz. Further analysis is needed to definitively relate the structure to transport properties.
Pacific Northwest National Laboratory (PNNL)
This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation. This project has also been made possible with support of the National Marine Sanctuary Foundation. The STAR program is administered by the Cal Poly Center for Excellence in Science and Mathematics Education (CESaME) on behalf of the California State University (CSU).