Intellectual Merit. The primary goal of this work is to develop an improved fundamental understanding of the transport mechanisms in porous ceramic based proton exchange membranes (PEMs). The performance of several types of fuel cells is limited by PEM performance, which has lead to a plethora of efforts to develop novel, high performance PEM materials. Standard materials used for such applications today are sulfonated perfluorcarbon polymers such as Nafion® whose greatest drawbacks include their poor performance at high temperatures (_80°C) and/or when not well hydrated. Inorganic solid acids, including some nanoporous ceramic materials, are among the novel membrane materials reported in the literature and have been demonstrated in the PI's lab to have greater proton conductivity and reduced fuel crossover flux as compared to Nafion®. It is expected that proton transport in such materials proceeds through both a bulk mechanism in the pores and a surface mechanism along the pore surfaces, with the relative importance of each dependent strongly on membrane properties such as surface area and surface acidity as well as environmental parameters such as pH and temperature. This work will systematically investigate the dependence of transport behavior in PEMS fabricated from modified porous alumina on such key variables. Physical and chemical characterization of the membranes will inform input files for molecular dynamics based simulations. Results of these simulations will be coupled with experimental measurements of transport behavior, primarily from impedance spectroscopy, to develop continuum and equivalent circuit models and determine relevant transport parameters such as diffusivities.
Broader Impacts. The proposed work will train graduate students in interdisciplinary research at the interface of two areas widely identified to be of critical importance to the United States: fuel cells and nanotechnology. While the immediate application of this work is to the development of PEM fuel cells for applications ranging from battery replacements for portable electronics to automotive engines, it will also impact a variety of sensor technologies which rely on ion conducting membranes. This project will also involve undergraduate students from both Louisiana Tech University and Grambling State University (GSU) through one of the PIs who has a joint appointment between the two universities. The a high percentage of African-American students for a non-HBCU (~15% of enrollment) at Louisiana Tech and at GSU, an HBCU, combined with concerted outreach efforts ensure that this project will have a significant impact on underrepresented minority groups in engineering and science in addition to enhancing partnerships between Louisiana Tech and Grambling. Additionally, the inclusion of undergraduate students in research activities will encourage these students to attend graduate school. This work will be performed in Louisiana, an EPSCOR state, impacting geographic diversity in scientific research. The PIs along with participating graduate and undergraduate students will present results from this project at national conferences in addition to participating in an ongoing nanotechnology seminar series at Louisiana Tech. These activities will serve both to disseminate results to a wide audience while also providing the students extremely valuable learning experiences and exposure, particularly for undergraduate students.
