자료유형  

 학위논문

Control Number  

0017161198

International Standard Book Number  

9798382761107

Dewey Decimal Classification Number  

540

Main Entry-Personal Name  

Greenstein, Emily P.

Publication, Distribution, etc. (Imprint  

[S.l.] : Northwestern University., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

184 p.

General Note  

Source: Dissertations Abstracts International, Volume: 85-11, Section: B.

General Note  

Advisor: Marks, Laurence D.;Poeppelmeier, Kenneth R.

Dissertation Note  

Thesis (Ph.D.)--Northwestern University, 2024.

Summary, Etc.  

요약Designing heterogeneous catalysts-those in which an active metal is supported on a high-surface area substrate-is a complex challenge owing to the many ways the metal and support can interact. Lanthanide scandates, a series of perovskites of the form LnScO3, are suited to studies of catalyst-support interactions because they retain many structure and property similarities as the lanthanide (Ln) is changed. Thorough characterization of a series of LnScO3 supports enables catalytic performance to be attributed to precise changes in properties of the support, thus eliminating the confounding variables that would otherwise obscure metal-support interactions. This dissertation demonstrates the effectiveness of a series of five LnScO3 (Ln = La, Pr, Nd, Sm, and Gd) through their synthesis, characterization, and catalytic testing. Synthesis of high-purity ( 96 mol%) LnScO3 is achieved via a hydrosauna approach guided by density functional theory (DFT). Hydrosauna synthesis applies humidity in an open system at near atmospheric pressure, in contrast to a typical sealed hydrothermal autoclave. In the hydrosauna method, too low water-vapor partial pressures inhibit LnScO3 particle growth, while an excess of water vapor results in undesired hydroxide and oxyhydroxide phases. The optimal humidity is shown to vary with the lanthanide in a non-monotonic manner: DFT is used to calculate the thermodynamics governing formation of undesired phases for each lanthanide, leading to precise prediction of the optimal water vapor pressure to synthesize faceted nanoparticles of each LnScO3. Guided by these predictions, the partial pressures were observed to range from 1.0 torr (for synthesis of LaScO3 and GdScO3) to 8.5 torr (for NdScO3 and SmScO3)-much lower than the humidity of a typical lab.DFT calculations for various LnScO3, as well as established X-ray photoelectron spectroscopy measurements, indicate that their electronic structure gives rise to the non-monotonic behavior across the support series. The proximity of Ln 4f states to the Fermi energy for each LnScO3 does not trend monotonically with the atomic number of the lanthanide but does correlate strongly with the strength of CO2 chemisorption to the LnScO3 surface. Pt/LnScO3 catalysts are tested using CO oxidation and reverse water-gas shift to observe that reaction rates across the LnScO3 series follow this non-monotonic trend in CO2 binding strength. The Ln 4f electrons may cause an inductive effect which in turn allows neighboring oxygen atoms at the surface to better donate charge to species adsorbed on the metal. The binding of CO to LnScO3-supported Pt metal is found to be governed by a combination of support effects, with contributions from both the electronic structure and the lattice parameter, which induces a strain at the Pt/LnScO3 interface.The consistent synthesis of well-faceted and highly phase pure LnScO3 nanoparticles, combined with the understanding of how LnScO3 electronic structure and properties change when varying the lanthanide ion, enables the use of the LnScO3 series to identify that strain affects Pt/LnScO3 monotonically while electronic effects do not. This library of materials can therefore be applied to other reactions as trends in catalytic performance across the LnScO3 series can indicate the most important properties for which to design new catalysts.

Subject Added Entry-Topical Term  

Chemistry.

Subject Added Entry-Topical Term  

Nanotechnology.

Subject Added Entry-Topical Term  

Materials science.

Subject Added Entry-Topical Term  

Engineering.

Index Term-Uncontrolled  

Heterogeneous catalysts

Index Term-Uncontrolled  

Density functional theory

Index Term-Uncontrolled  

Electron microscopy

Index Term-Uncontrolled  

Nanoparticles

Index Term-Uncontrolled  

Photoelectron spectroscopy

Added Entry-Corporate Name  

Northwestern University Materials Science and Engineering

Host Item Entry  

Dissertations Abstracts International. 85-11B.

Electronic Location and Access  

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Control Number  

joongbu:656388