Towards the Rational Design of Supported-Bimetallic Nanoparticle Catalysts
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1217-Y01-07
Towards the Rational Design of Supported-Bimetallic Nanoparticle Catalysts Priyabrat Dash and Robert W. J. Scott* Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N 5C9. ABSTRACT Heterogeneous catalysts consisting of nanoparticles dispersed on an oxide support are a mainstay in industrial reactions, and are often made via thermal reduction of metal salts dispersed onto a pre-synthesized support. Herein we document a route towards the design of xerogel-supported nanoparticle catalysts by trapping compositionally-tuned polymer-stabilized nanoparticle precursors into sol-gel matrices. Such a route allows in principle for the tuning of the size, composition, architecture, and electronic properties of nanoparticle catalysts, which allows for the development of highly efficient and selective catalysts. As proof of concept we detail the synthesis of co-reduced PdAu nanoparticles in titania supports. The final materials are well-characterized by HRTEM and energy dispersive spectroscopy (EDS), which confirm the compositional uniformity of the nanoparticles. The importance of controlling calcination conditions in order to retain designed nanoparticle compositions is stressed; high temperature calcination conditions lead to a large degree of sintering and loss of compositional uniformity, while mild calcination temperatures can be used to retain nanoparticle compositions and sizes. INTRODUCTION Supported metallic nanoparticle catalysts have attracted a lot of interest as they show increased catalytic activity and selectivity in different reactions of practical importance.[1,2] Traditional synthetic routes involve impregnating metal salts onto high-surface area supports, followed by various thermal activation steps.[3] The main pitfall of these routes is control over size, structure, and composition which is particularly challenging in the case of bimetallic catalysts.[4] Recent advances in nanoparticle preparation techniques offer a new direction in the synthesis of supported nanoparticle catalysts.[5] Chemical routes towards supported-nanoparticle catalysts are desired because of excellent tuning of composition and structure of nanoparticles. Keeping this in mind, we sought to investigate routes towards the synthesis of supported nanoparticle catalysts where the size, structure, and composition can be maintained in both metallic and bimetallic nanoparticle catalysts. Among the various techniques available for the synthesis of supported-bimetallic nanoparticle catalysts, the method of entrapping pre-prepared nanoparticles into an inorganic matrix by the sol-gel method is particularly attractive.[6,7] This method can provide a general route to synthesize supported bimetallic catalysts which are nearly monodisperse in size and composition. This can lead to a better understanding of structureactivity relationships in such catalysts, which is essential for the exploitation of the synergistic properties of bimetallic nanoparticles in catalytic reactions. Considering these benefits
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