T. Zawodzinski, Jr.
University of Tennesse-Knoxville,
United States
Keywords: fuel cell, hydrogen, truck
Summary:
In this contribution, a review of the efforts to improve membranes for fuel cells to be used in heavy duty vehicles will be presented. More specifically, we will provide a critical review efforts to develop membranes for operation up to 120oC, with special focus on operation at 50% RH or lower and efforts to use hydrocarbon (HC) membranes to circumvent the perceived issues with PFAS. Obtaining a membrane for the ‘Million Mile Fuel Cell Truck’ entails addressing several challenges that must simultaneously be met, including dimensional stability of the membranes, suitable mechanical properties and, of course, low membrane resistance in the cell.We will present an overview of the conductivity of simple perfluorinated and non-perfluorinated (HC) membranes as a function of pH. In general, the HC membrane show precipitous decreases in conductivity at RH < 70% (roughly). We will describe the underlying chemical factors that likely led to this. Then we discuss several avenues that we have used in attempts to address this issue, including manipulating the introduction of the acid functionality in the membrane and developing composite material structures. Since conductivity is not the only issue to be addressed, we will also provide context on the mechanical and swelling properties of the membranes. Finally, some thoughts on next steps will be presented in the context of the limitations of the various approaches.