Precision synthesis with atomic layer deposition for oxygen reduction reaction enhancement
Abstract/Contents
- Abstract
- Proton-exchange-membrane fuel cell (PEMFC) technology has progressed significantly over the past few decades for CO2-free energy conversion. However, the energy efficiency of PEMFCs is still far below the thermodynamic limit for numerous reasons. A major cause is the overpotential induced by the sluggish reaction kinetics, especially for oxygen reduction reaction (ORR) on the cathode. To overcome the limitation, efforts have been devoted to developing catalyst material structure engineering to maintain a high intrinsic catalytic activity. In this thesis, I will firstly discuss a strained Pt catalyst with an enhanced catalytic activity for ORR. The catalyst was fabricated by sequential atomic layer deposition(ALD) of cobalt oxide and Pt on the carbon supports, followed by acid leaching that removes almost the entire cobalt oxide template. A compressive strain in the Pt-Pt lattice of the strained catalyst was observed by both extended x-ray absorption fine structure and high-resolution transmission electron microscopy in which negligible Pt-Co interaction is found. Therefore the performance enhancement is mostly attributed to the Pt lattice strain. Secondly I will introduce a precision alloyed Pt-Ti catalyst with a Ti-rich subsurface layer. This catalyst structure was found to have a higher confidence level regarding significant catalytic activity enhancement in density functional theory model. An almost 8-fold activity enhancement compared to Pt ALD catalyst were achieved. Both dynamic secondary ion mass spectroscopy and scanning transmission electron microscopy indicate significant Ti enrichment close to the very surface. Finally, I will describe the fabrication and performance of strained Pt catalyst and Pt-Ti alloy catalyst integrated in membrane electrode assembly(MEA). To further improve the mass activity of the strained Pt catalyst, passivation gas incorporated atomic layer deposition (PALD) was applied. The mass activity was pushed to 0.59A/mg on a Ketjen Black carbon support and even close to 0.8 A/mg on CMK-3. The Ketjen Black-supported catalyst additionally demonstrated impressive durability. For Pt-Ti alloy catalyst, significant performance enhancement especially in specific activity was demonstrated. The temperature-dependent performance was studied and the Pt-Ti alloy catalyst indicates improvement in ORR performance mainly attribute to lowered activation energy barrier.
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 | Wang, Zhaoxuan |
|---|---|
| Degree supervisor | Prinz, F. B |
| Thesis advisor | Prinz, F. B |
| Thesis advisor | Clemens, B. M. (Bruce M.) |
| Thesis advisor | Zheng, Xiaolin, 1978- |
| Degree committee member | Clemens, B. M. (Bruce M.) |
| Degree committee member | Zheng, Xiaolin, 1978- |
| Associated with | Stanford University, Department of Materials Science and Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Zhaoxuan Wang. |
|---|---|
| Note | Submitted to the Department of Materials Science and Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2020. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2020 by Zhaoxuan Wang
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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