Structure, oxidation, and catalytic activity of platinum-tin surfaces
(2024)- Abstract
- This thesis work has focused on the platinum-tin surface, especially how it behaves when exposed to gases like oxygen and carbon monoxide. Platinum-tin is used as a catalyst for a range of reactions, including the oxidation of carbon monoxide at mild conditions, which is important for gas purification in fuel cells. The platinum-tin alloy has properties useful for the reactions it catalyses, but it is known that the tin in the catalyst oxidises during reaction conditions. What is not known is what roles these oxides play in the reactions.
Our efforts have been spent on trying to understand the oxide phases that form on the platinum-tin surface and how they behave under CO oxidation conditions. We have studied two related surface oxides... (More) - This thesis work has focused on the platinum-tin surface, especially how it behaves when exposed to gases like oxygen and carbon monoxide. Platinum-tin is used as a catalyst for a range of reactions, including the oxidation of carbon monoxide at mild conditions, which is important for gas purification in fuel cells. The platinum-tin alloy has properties useful for the reactions it catalyses, but it is known that the tin in the catalyst oxidises during reaction conditions. What is not known is what roles these oxides play in the reactions.
Our efforts have been spent on trying to understand the oxide phases that form on the platinum-tin surface and how they behave under CO oxidation conditions. We have studied two related surface oxides with (4 × 4) and (2m × 2n) periodicities in ultra high vacuum conditions. They form during the initial stages of oxidation on the Pt3Sn(111) surface with the (2m × 2n) oxide having a higher oxygen content than the (4 × 4) oxide. The growth and transformations of these oxides was studied using scanning tunnelling microscopy, low energy electron microscopy and low energy electron diffraction, surface x-ray diffraction and density functional theory. Transformations between these oxides are driven by exposure to oxygen or carbon monoxide, indicating that they may have a role in the CO oxidation reaction.
We have also studied platinum-tin surfaces operando during CO oxidation at millibar pressures. The tin in the platinum-tin surface oxidises under reaction conditions and this lowers the activity of the surface. The oxidised platinum-tin surfaces are more active for CO oxidation than the platinum surfaces studied, and the activity is linked to platinum-tin alloy or Sn(II) surface oxides. The gas composition and pressure affects the composition and morphology of the oxide that forms, and at sufficient temperatures CO can reduce the tin oxides. This reduction requires exposed oxide edge sites. The reduction of the tin oxides does not appear to be a main contributor to the
CO oxidation activity. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/08e82b62-3542-4036-b3a8-281eed304c06
- author
- Wallander, Harald LU
- supervisor
- opponent
-
- Dr. Starr, David, Institute Solare Brennstoffe, Helmholtz Zentrum, Berlin
- organization
- alternative title
- Struktur, oxidation och katalytisk aktivitet hos platina-tennytor
- publishing date
- 2024-09-10
- type
- Thesis
- publication status
- published
- subject
- keywords
- ytfysik, katalys, platina, tenn, CO oxidation, XPS, XAS, SXRD, STM, DFT, surface science, catalysis, platinum, tin, CO oxidation, XPS, XAS, SXRD, STM, DFT, Fysicumarkivet A:2024: Wallander
- pages
- 179 pages
- publisher
- Lunds universitet
- defense location
- Rydbergsalen, Department of Physics. Join via Zoom: https://lu-se.zoom.us/j/63862186834
- defense date
- 2024-10-04 13:15:00
- ISBN
- 978-91-8104-156-9
- 978-91-8104-155-2
- language
- English
- LU publication?
- yes
- id
- 08e82b62-3542-4036-b3a8-281eed304c06
- date added to LUP
- 2024-09-10 16:49:50
- date last changed
- 2025-04-04 14:18:01
@phdthesis{08e82b62-3542-4036-b3a8-281eed304c06,
abstract = {{This thesis work has focused on the platinum-tin surface, especially how it behaves when exposed to gases like oxygen and carbon monoxide. Platinum-tin is used as a catalyst for a range of reactions, including the oxidation of carbon monoxide at mild conditions, which is important for gas purification in fuel cells. The platinum-tin alloy has properties useful for the reactions it catalyses, but it is known that the tin in the catalyst oxidises during reaction conditions. What is not known is what roles these oxides play in the reactions.<br/>Our efforts have been spent on trying to understand the oxide phases that form on the platinum-tin surface and how they behave under CO oxidation conditions. We have studied two related surface oxides with (4 × 4) and (2m × 2n) periodicities in ultra high vacuum conditions. They form during the initial stages of oxidation on the Pt3Sn(111) surface with the (2m × 2n) oxide having a higher oxygen content than the (4 × 4) oxide. The growth and transformations of these oxides was studied using scanning tunnelling microscopy, low energy electron microscopy and low energy electron diffraction, surface x-ray diffraction and density functional theory. Transformations between these oxides are driven by exposure to oxygen or carbon monoxide, indicating that they may have a role in the CO oxidation reaction.<br/>We have also studied platinum-tin surfaces operando during CO oxidation at millibar pressures. The tin in the platinum-tin surface oxidises under reaction conditions and this lowers the activity of the surface. The oxidised platinum-tin surfaces are more active for CO oxidation than the platinum surfaces studied, and the activity is linked to platinum-tin alloy or Sn(II) surface oxides. The gas composition and pressure affects the composition and morphology of the oxide that forms, and at sufficient temperatures CO can reduce the tin oxides. This reduction requires exposed oxide edge sites. The reduction of the tin oxides does not appear to be a main contributor to the<br/>CO oxidation activity.}},
author = {{Wallander, Harald}},
isbn = {{978-91-8104-156-9}},
keywords = {{ytfysik; katalys; platina; tenn; CO oxidation; XPS; XAS; SXRD; STM; DFT; surface science; catalysis; platinum; tin; CO oxidation; XPS; XAS; SXRD; STM; DFT; Fysicumarkivet A:2024: Wallander}},
language = {{eng}},
month = {{09}},
publisher = {{Lunds universitet}},
school = {{Lund University}},
title = {{Structure, oxidation, and catalytic activity of platinum-tin surfaces}},
url = {{https://lup.lub.lu.se/search/files/194891779/Harald_Wallander_-_WEBB.pdf}},
year = {{2024}},
}