High Temperature PEM Fuel Cells Based on Ion-Pair Systems

Current commercial proton exchange membrane fuel cell technology typically employs perfluorosulfonic acid polymer-based membranes due to their good durability and high proton conductivity. However, the membranes are expensive and have limited operating conditions, operating only up to 80 °C with high relative humidity conditions, while the preferred maximum operating temperature of The Department of Energy is 120°C. In addition, the perfluorinated polymers have health and environmental concerns. Therefore, next generation proton exchange membranes are necessary to satisfy several important key properties: high proton conductivity, high durability, low-cost, fluorine-free, and functionality at 120 °C. In Phase I, we will develop novel QA-functionalized exchange membranes meeting the key properties. The membranes will have phosphoric acid doped system using the acid as a proton conduction medium instead of the water of the perfluorosulfonic acid polymer-based membranes, which will allow operating temperature from ambient temperature up to 180 °C without any humidification. Humidification is needed in the current technology adding cost, while still having issues with PA leaching. The new membrane design adopts quaternary ammonium-phosphate ion-pair interaction for better phosphoric acid retention in the membrane. Fuel cells that can function at the temperature range of 80-180 °C would be significantly beneficial for both stationary and transportation applications as they donĺt need complex water and heat management systems and fuel purification system. Moreover, high humidity tolerance of ion-pair interaction will make frequent startup/shutdown of fuel cell convenient and allow to function over the full range of automotive operating conditions. Transportation will be one of the largest end-use segments for hydrogen in 2050. Transportation sectors contributes about 19% of global carbon emission today. Among them, heavy-duty trucks, regional trains, buses, and long-range passenger vehicles are difficult to run by lithium ion battery technology. Particularly, heavy-duty trucks are expected to be the largest consumer of hydrogen in long-term due to their long mileage between charges and short recharging time. In 2030, the share of the global fuel cell heavy-duty truck sales is expected to be 11%, which could eliminate about 60 million metric tons of CO2 emissions in that year.