Molecular modeling of interfacial structure and dynamics in proton conductors for fuel cells

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This program in theory and molecular modeling explores proton transport along hydrated interfaces with dense packing of proton binding surface groups. These phenomenona are vital for a wide range of areas, including proton motion along cellular membranes in bioenergetics as well as energy conversion in hydrogen fuel cells. Our main interest lies in the latter realm.    Fuel cells are highly efficient and environmentally benign electrochemical energy converters. They are under intensive research for applications in vehicular transportation and many devices requiring portable power. Tremendous efforts in fuel cell research focus on the development of advanced polymer electrolyte membranes with high proton conductivities, high stability, good water retention, and low cost.    Our main objective is to contribute to the fundamental understanding of structure-property relationships in proton conducting media. Thereby, we approach the long-standing goal of establishing a theoretical framework for the rational design of advanced fuel cell membranes. For our studies of proton transport mechanisms we employ a lowly hydrated regular 2D array of charged surface groups as a model system. We utilize full ab-initio molecular dynamics calculations to unravel pathways of long-range proton transport in these model structures. In order to overcome the disparity of time scales between molecular motions and the occurence of proton transfer events we employ transition path sampling techniques. Activation energies and rates of proton transport are calculated. Results of our calculations furnish relations between  proton mobility and controlled structural parameters of the interfacial array (e.g. chemical composition of the polymer, length and density of surface groups).         This program provides excellent training possibilities for students. They learn how to use pertinent tools in theoretical physics and chemistry and apply them to foremost challenges in fuel cell research and electrochemical materials science.