Modeling catalytic properties of metal nanoparticles
Abstract/Contents
- Abstract
- Catalysts are materials that can accelerate chemical reactions, and they are key to creating sustainable processes and a greener environment. Catalysts in the form of metal nanoparticles are ubiquitous in current industrial processes, and they are critical to creating a sustainable energy future. Theory has provided vital insights into the fundamental limitations of various types of processes, and density functional theory (DFT) calculations have inspired the discovery of new active materials. Advancements in supercomputing resources and scalable quantum chemistry codes have enabled us to explore the catalytic behavior of metal nanoparticles from the fundamental atomic level. We present calculated adsorption energies of oxygen on gold and platinum clusters with up to 923 atoms (3 nm diameter) using Density Functional Theory. We find that surface tension of the clusters induces a compression of which weakens the bonding of adsorbates compared to the bonding on extended surfaces. The effect is largest for close packed surfaces and almost non-existent on the more reactive steps and edges. The effect is largest at low coverage and decreases, even changing sign, at higher coverages where the strain changes from compressive to tensile. Quantum-size-effects also influence adsorption energies but only below a critical size of 1.5 nm for platinum and 2.5 nm for gold. We develop a model to describe the strain-induced size effects on adsorption energies, which is able to describe the influence of surface structure, adsorbate, metal, and coverage. Stability of metal nanoparticle is also a great concern in the field of heterogeneous, and a dominant process that degrades the activity of these catalysts is the agglomeration of individual nanoparticles. In order to better understand the sintering mechanism, we propose a kinetic Monte-Carlo (kMC) model for simulating the movement of platinum particles on supports, based on atom-by-atom diffusion on the surface the particle. The proposed model was able to reproduce equilibrium cluster shapes predicted using Wulff-construction. The diffusivity of platinum particles was simulated both purely based on random motion and assisted using a drift velocity. The overall particle diffusivity increases with temperature, however the extracted activation barrier appears to be temperature independent. In addition, this barrier was found to increase with particle size, as well as, with the adhesion between the particle and the support.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Li, Lin |
|---|---|
| Associated with | Stanford University, Department of Chemistry. |
| Primary advisor | Nørskov, Jens K |
| Thesis advisor | Nørskov, Jens K |
| Thesis advisor | Abild-Pedersen, Frank |
| Thesis advisor | Martinez, Todd J. (Todd Joseph), 1968- |
| Advisor | Abild-Pedersen, Frank |
| Advisor | Martinez, Todd J. (Todd Joseph), 1968- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Lin Li. |
|---|---|
| Note | Submitted to the Department of Chemistry. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Lin Li
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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