Computational Study of Mechanisms of Fuel Cell Membrane Degradation

Stevens, Jonathan, Kim Utterbeck, and Malcolm Spicer

~~PEMFCs, or Polymer Electrolyte Membrane Fuel Cells, or simply “Fuel Cells” , are expected to continue to play a role in the ongoing development of applied alternative energy sources The fuel cell membrane should be a stable material able to withstand physical stresses, wide variations of temperature, and degradation by chemical agents. The reactions of membranes with radicals such as OH and H are of particular interest as these are expected to be present in the process of a fuel cell’s operation.
Typically, fluorinated polymers such as Nafion have been considered for use in fuel cells. Nafion is a physically stable material, but it is relatively costlyand degradation/oxidation products may have a negative impact on the environment. For these reasons, nonfluorinated materials have been proposed for polymer electrolyte membranes.  Sulfonated polyether(ether) ketone, or sulfonated PEEK, or sPEEK membranes are one possible candidate for fuel cell membranes; Polyethersulfones (PSUs) can also be used to create proton-exchanging membranes.  While studies suggest these materials are physically stable, questions remain over the chemical stability of such membranes, particularly in the presence of H and OH radicals.
Our group’s research to implements molecular orbital and density functional calculations to study the attack of OH and of of H radicals on these polymers,  Due to the large number of electrons to be modeled in the complete polymer, our group studies the chemistry of small model compounds of sPEEK and PSU.  Preliminary results of these calculations will be presented.