Thermally Stable Nanoporous Membrane For PEM Fuel Cell Operated at High Temperatures

This proposal addresses the limitations of hydrocarbon ionomers in proton exchange membranes (PEM) fuel cells. PEM fuel cells operate below 90ºC with a relative humidity greater than 70% because their perfluorosulfonic acid (PFSA) based membrane needs to stay hydrated. As a result, current PEMFCs are expensive because they need a high platinum-group metal (PGM) loading, an effective humidification mechanism, and a good heat rejection. These problems could be solved by replacing the PFSA-typed membrane with a high-temperature PEM membrane that allows the fuel cells to operate above 120ºC. This project will develop a thermally stable, proton-conductive, nanoporous polymer membrane for PEM fuel cells. The nanoporous polymer with interconnected ionic channels will contain and stabilize the doped phosphoric, which produces high proton conductivity even at elevated temperatures. In addition, the polymer material will be highly crosslinked to prevent membrane swelling and to resist hydrogen and oxygen crossover. In Phase I, TDA will prepare these polymers, modify their geometry, and characterize their phase formation using small-angle XRD. After coating and polymerization, we will measure the membrane mechanical properties, proton conductivity, and hydrogen crossover and correlate them to the resulting nanoporous structure. The membrane processing methods will also be varied, and process-structure-property relationships will be used to guide our development of these new membrane materials for high-temperature PEMFCs. We will use the most promising structured polymers to make membranes and prepare membrane electrode assemblies (MEAs) to test in a lab-scale fuel cell (5 cm2) using hydrogen fuel and oxygen (or air). In Phase II, we will further improve our membranes, perform extended membrane durability in a hydrogen fuel cell operated at 160ºC, and scale up the production of PEMs in preparation for commercial sales. Commercial Applications include proton exchange membranes used in zero-emission vehicles and stationary fuel cell systems.