In situ visualization and nanophotonic control of hydrogen-driven nanoscale phase transformation dynamics
Abstract/Contents
- Abstract
- Understanding and manipulating chemically-driven nanoparticle transformations is crucial for the efficacy of next-generation energy storage and catalytic materials. However, obtaining such control is an outstanding challenge. Notably, there is a mismatch in length-scale between the atomic-scale structural features (such as atomic coordination number and surface strain) which influence transformation dynamics and the extrinsic parameters (such as temperature, chemical composition, and chemical environment) that can be controlled. In this thesis, I explore how optical excitation can be used to enable new catalytic mechanisms. In particular, we utilize local surface plasmon resonances (LSPRs), which result in strong optical enhancement, local temperature gradients, and hot carrier populations, to control chemical transformations. These LSPRs enable chemical activity that is no longer solely defined by inherent nanoparticle structure but rather by the local electromagnetic field. We use a suite of in situ environmental transmission electron microscopy techniques to visualize a model reaction: the hydrogenation and dehydrogenation phase transformation of individual palladium hydride (PdHx) nanoparticles. First, I describe the mechanism of this phase transition without plasmonic excitation. By visualizing the phase transformation dynamics in distinctly-faceted nanoparticles, including single-crystalline cubes and octahedra, we find that the new phase always nucleates at nanoparticle tips and corners. Then, I demonstrate how LSPRs can modify the preferred active site using a proof-of-concept crossed-bar Au-PdHx system. Under resonant illumination, we observe new nucleation sites and dynamics at the nanoscale, which we experimentally and computationally verify to be energetically unfavorable. Our work shows how plasmons enable catalytic site-selectivity and new reaction mechanisms, with important implications spanning catalysis, energy, and information.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2020; ©2020 |
| Publication date | 2020; 2020 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Sytwu, Katherine Lee |
|---|---|
| Degree supervisor | Byer, R. L. (Robert L.), 1942- |
| Degree supervisor | Dionne, Jennifer Anne |
| Thesis advisor | Byer, R. L. (Robert L.), 1942- |
| Thesis advisor | Dionne, Jennifer Anne |
| Thesis advisor | Brongersma, Mark L |
| Degree committee member | Brongersma, Mark L |
| Associated with | Stanford University, Department of Applied Physics |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Katherine Sytwu. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Thesis Ph.D. Stanford University 2020. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2020 by Katherine Lee Sytwu
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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