Final Report - Membranes and MEA's for Dry, Hot Operating Conditions

U.S. DOE Progress Towards Developing Low-Cost, High Performance, Durable Polymer Electrolyte Membranes for Fuel Cell Applications

“… a Status represents PFIA membrane as described in [ 9 ]; b Tested in MEA at 1 atm O 2 or H 2 at nominal stack operating temperature, humidified gases at 0.5 V DC; c Costs projected to high-volume production (500,000 stacks per year); d Based on U.S. DRIVE Fuel Cell Tech Team Cell Component Accelerated Stress Test as described in [ 10 ]. …”

“…One approach to achieving low equivalent weight without sacrificing mechanical properties involves the incorporation of multiple proton donors per side chain. This approach has been investigated at 3M using PFSA-type polymers, based on 3M’s existing ionomer chemistry, which were modified to include multiple acid sites on the polymer side chain while maintaining the same TFE backbone [ 9 , 17 , 30 , 31 ]. The existing 3M ionomer contains 4-carbon side sulfonated side chains attached to the TFE backbone through an ether linkage.…”

“…3M had previously investigated reduction in EW through increasing the density of side chains, but while the low EW polymers performed well at low RH, the low backbone crystallinity and high water uptake of these polymers resulted in poor mechanical properties and high water solubility at elevated temperatures. To bypass this shortcoming, 3M developed ionomers with multiple acid groups per side chain, thus providing a high density of acid groups while maintaining the long TFE backbone segments required for crystallinity [ 9 , 31 ]. 3M investigated several approaches to introduce multiple acid groups per side chain, but achieved the best results by incorporating a superacid bis sulfonyl imide group within the side chain [ 17 ].…”

“…Mechanical stability of the PFIA ionomer was improved using a chemically inert nanofiber support which reduced linear swelling in water by as much as 15-fold [ 9 , 31 ]. The supported and chemically stabilized PFIA membrane was subjected to the DOE membrane durability tests, where it exceeded 20,000 RH cycles in the mechanical durability test and lasted over 600 h at OCV in the chemical durability test, exceeding the DOE targets.…”

Fuel Cell Performance of Electrospun Membranes with 660 Equivalent Weight Perfluorosulfonic Acid

“…One example of a high IEC PFSA is 3M Company's 580EW polymer. This polymer has a proton conductivity of 146 mS/cm at 120 o C and 50% relative humidity (RH), compared to 37 mS/cm for 1100EW Nafion at the same conditions (4). However, the drawback of such high IEC polymers is that they swell excessively in water with a loss in mechanical properties and long-term dimensional stability or become water soluble.…”