Multiple applications in renewable energy, including direct fuel cells and biomass reforming, rely on aqueous phase heterogeneously-catalyzed reactions. Often, these applications use expensive transition metal catalysts, such as platinum or platinum alloys. A goal of our work is to understand the molecular-level ways in which these catalysts function, so that we may design less expensive catalysts for these (and other) applications. An important part of understanding catalyst function in aqueous phase heterogeneous catalysis is understanding the role of H2O. Experiments and simulations have uncovered a variety of ways in which H2O molecules influence surface phenomena in aqueous phase heterogeneous catalysis. For example, they alter reaction intermediate and transition state energies, co-catalyze certain reaction steps, and control which catalytic pathways are followed. In this work, we use multiscale modeling to examine how the structure of liquid water at the catalyst interface influences the mechanism of Pt-catalyzed sugar alcohol conversions, which are important in biomass upgrading and direct methanol fuel cells. Specifically, we show how the structure of liquid water influences the energies of catalytic surface intermediates and transition states and the frequency factors and activation barriers of catalytic reactions. We show that hydrogen bonding between liquid water and catalytic species influences these quantities significantly and determines the extent to which H2O molecules participate in the catalysis.

Molecular-level insights into the role of water on the chemistry of sugar alcohol decompositions revealed by multiscale modeling

256th National Meeting (2018)

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