Date of Award

Summer 2019

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Donna A. Chen

Abstract

The dissertation is focused on understanding the growth, morphology and activity of model heterogeneous catalytic surfaces. Vapor deposited metal clusters on single crystal surfaces are well-defined systems that can be used to understand the growth, composition and activity relationships in commercial catalysts. A fundamental understanding of surface reactions is required in order to provide insight into the development of new catalytic materials. The model catalysts approach allows for systematic investigations due to excellent control over growth, composition and characterization under a carefully controlled ultrahigh vacuum (UHV) environment.

The nucleation, growth and chemical activity of monometallic and bimetallic Pt-Re clusters on highly oriented pyrolytic graphite (HOPG) were investigated in comparison to clusters supported on TiO2(110) and Pt(111) single crystal in order to understand the role of support on the activity for the water gas shift (WGS) reaction. And studies were also addressed how activity is influenced by cluster sizes, interactions with the support and surface compositions of the bimetallic clusters. For the WGS reaction, bimetallic clusters consisting of a Re core and Pt shell, have higher WGS activity than turnover frequency (TOF) of pure Pt. Enhanced WGS activity is reported on the TiO2(110) support suggesting that the support promotes WGS activity.

The limited nature of fossil fuel resources has led to the pursuit of renewable energy sources for the sustainable production of fuels and fine chemicals. Catalytic processes are needed for transforming biomass derived materials into commodity chemicals where furfural to furfuryl alcohol is an important process. It is a challenging task to selectively hydrogenate C=O to the unsaturated alcohol due to the presence of two different types of unsaturated chemical bonds (C=C and C=O) in the aldehyde. The supported Pt-Sn catalytic system has attracted particular attention due to its preferential activation of the C=O bond in unsaturated aldehydes to improve selectivity to unsaturated alcohols. The nucleation, growth and surface composition of Pt-Sn clusters grown on TiO2(110) and Sn/Pt(111) surfaces were studied using surface analysis techniques such as scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS) and low energy electron diffraction (LEED).

Rights

© 2019, Thathsara Deshani Maddumapatabandi

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