Atomistic Simulations of Alternative Proton Exchange Membranes for Fuel Cell Applications

SPEEK (Sulfonated Poly(ether ether ketone)) membranes constitute promising alternatives to nafion for DMFC(Direct Methanol Fuel Cell) applications. In this talk, the results of extensive all-atom simulations of water and methanol solvated SPEEK membranes are reported. We focus on key features of changes in structure, transport and the corresponding coupling between the structure and transport. Our simulations suggest that the membrane swells appreciably with increasing water and methanol contents. The sizes of water clusters in the membrane are found to be appreciably lower than that reported for nafion in the literature, thus confirming experimental observations of narrower aqueous channels in SPEEK than nafion. The diffusivities of water, hydronium ions and methanol are also found to be lower than those published for nafion earlier, thus complementing experimental findings of lower penetrant mobility in SPEEK than nafion. Structural information pertaining to the relative locations of methanol and hydronium ions is determined.