Understanding the Chemical Activity of Oxide-supported Bimetallic Clusters

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In this project funded by the Chemical Catalysis Program in the Division of Chemistry, Professors Donna Chen and John Monnier will study titania-supported Pt-Re clusters as model systems for developing new catalysts for the conversion of bio-renewable fuels like ethanol to clean H2 for use in fuel cells. The proposed studies will guide the development of superior Pt-Re/TiO2 catalysts by providing fundamental understanding of how surface chemistry is controlled by: bimetallic interactions, reactions occurring at the metal-cluster interface, the activity of oxidized Re, and the dependence of these properties on cluster size. In addition, the proposed work will provide detailed knowledge of reaction kinetics, mechanisms and the nature of the active sites. Oxidative reforming of ethanol with O2 and water (autothermal reforming) will be investigated on vapor-deposited Pt, Re, and Pt-Re clusters prepared in ultrahigh vacuum. Partial oxidation of ethanol and the water-gas shift reaction will be studied on the model catalysts to independently investigate these two reactions, which both occur in autothermal reforming. The bimetallic cluster surfaces will be fully characterized using techniques such as scanning tunneling microscopy, low energy ion scattering, X-ray photoelectron spectroscopy, temperature programmed desorption and high resolution transmission electron microscopy. The catalytic activities of the clusters will be investigated using a recirculation loop reactor coupled to the UHV system, and surface intermediates will be studied under catalytic conditions using infrared reflection absorption spectroscopy. The PIs will train graduate and undergraduate students in the areas of surface science and catalysis, and more importantly in the area of overlap between surface science and catalyst performance. Furthermore, the PIs will actively participate in efforts to promote understanding of nanoscience and nanotechnology research in the local community via existing programs at USC.Many commercial heterogeneous catalysts consist of bimetallic materials on oxide support surfaces. This research project will lead to better understanding of how catalytic activity can be tailored through interactions between the two metals and interactions between the metals and the support. Specifically, this work will contribute to the rational design of platinum and rhenium containing catalysts for the decomposition of renewable biofuels like ethanol to clean hydrogen for use in hydrogen fuel cells. Furthermore, the PIs will actively participate in efforts to promote understanding of nanoscience and nanotechnology research in the local community via existing programs at USC.