Probing the Structure-property Relationship of Core/Shell Bimetal Nanoparticles as a Model Catalyst

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AbstractTechnical ImpactThe combination of two metals to make a bimetallic catalyst frequently leads to a more catalytically active material than either constituent metal. Besides higher activities, bimetallic catalysts can have improved selectivities and greater deactivation resistance. The catalytic chemistry that explains how bimetallic enhancement arises is not well explained. Depending on the chemical reaction, the enhancement can be attributed to a geometric effect, an electronic effect, or a mixed metal site effect. The difficulties in determining the source of catalytic enhancement are numerous: enhancement could be due to a combination of these effects; the bimetallic nanostructure is not well-controlled at the synthesis level; there may be a metal-support interaction; or the studied bimetallic nanostructure can reconfigure during the chemical reaction.So, how to develop a greater understanding of bimetallic catalysts so that they may be exploited appropriately is a significant question. Professor Michael Wong at William Marsh Rice University in Houston has an approach to developing more of this understanding. Wong intends to focus on a model of a bimetallic catalyst in which metallic nanoparticles of one metal are the support for the second active metal. The interaction is built-in and controllable, and amenable to the analysis of the bimetallic nanostructure using spectroscopic methods near reaction conditions; and culminating in the quantification of their catalytic properties under reaction conditions that do not modify the nanostructure. The model system is based on previous studies using palladium metal supported on gold nanoparticles, and the model test reaction is the catalysis in the water phase of trichloroethene hydrodechlorination. Continued innovations in catalysis technology rely on the development of novel materials and the rigorous elucidation of reactivity dependence on catalyst nanostructure.PdAu bimetallic catalysis has shown some promise as a new technology for water-phase hydrodechlorination. This technology is important for pollution control in groundwater, a source for 50% of US drinking water.Broader ImpactThis proposal describes a three-year research and teaching plan consisting of multidisciplinary training of graduate and undergraduate students in materials chemistry, heterogeneous catalysis, chemical engineering fundamentals, and colloid science. Three new educational and community outreach activities are proposed: a yearly NanoDays demonstration at the Children's Museum of Houston, a local-area high school teachers development program in coordination with the NSF-sponsored RET program at Rice, and a lab module design project incorporated into the graduate-level kinetics/reactor engineering course. This award is being funded jointly by the CBET Catalysis and Biocatalysis Program and the CHE Catalysis Program.