Segmented and Blocky Hydrocarbon Ion Pair Membranes for Fuel Cells

The DOE has identified a need for thin and durable proton conducting membranes that offer enhanced energy efficiency to power zero emission vehicles. Specifically, a cost effective hydrocarbon-based alternative to expensive commercial perfluorosulfonic acid ionomers are sought. Current hydrocarbon membranes do not meet the performance or durability needed in the conditions for transportation fuel cells, operating at 120 °C. The objective of the proposed STTR is to develop and demonstrate thermally stable hydrocarbon based membranes that meet the chemical and mechanical stabilities necessary for the demanding environments and durability for high startup cycles. The approach involves the synthesis of novel segmented hydrocarbon polymers for new ion pair complexed membranes. In Phase I, quaternary ammonium-functionalized segmented polymers with controlled molecular weight(s) shall be synthesized to develop membranes with tailorable morphology. The quaternary ammonium groups will be use to form ion pairs with imbibbed phosphoric acid. The ion pair formation via a controlled imbibbing process yield proton conduction membranes with good acid retention. The phase separated morphology may enhance the proton conductivity while directly influencing phosphoric acid location (i.e., phosphoric acid will preferentially concentrate in the hydrophilic phase with the quaternary ammonium groups). Proton conductivity shall be evaluated as a function of percent quaternary ammonium functionalization and morphology under a wide range of fuel cell vehicle operating conditions, including humidity and temperature. The proton diffusion and transport properties shall be investigated in the ion pair membranes. The membrane prototypes will be evaluated for film formation and quality, thermooxidative and chemical stabilities, mechanical durability and preliminary fuel cell test shall set a Technology Readiness Level of 6-7. Short term fuel cell durability testing at an Independent National Laboratory shall be performed on downselected membranes.Durable, thermally stable proton conducting hydrocarbon ion pair based membranes shall be commercialized primarily as fuel cell membranes. These membranes are directly applicable in stationary power applications as well as water purification/desalinization applications.