Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Dehydrogenation of methanol on Cu2O(100) and (111)
Stockholm University, Faculty of Science, Department of Physics.
Show others and affiliations
Number of Authors: 102017 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 24, article id 244702Article in journal (Refereed) Published
Abstract [en]

Adsorption and desorption of methanol on the (111) and (100) surfaces of Cu2O have been studied using high-resolution photoelectron spectroscopy in the temperature range 120-620 K, in combination with density functional theory calculations and sum frequency generation spectroscopy. The bare (100) surface exhibits a (3,0; 1,1) reconstruction but restructures during the adsorption process into a Cu-dimer geometry stabilized by methoxy and hydrogen binding in Cu-bridge sites. During the restructuring process, oxygen atoms from the bulk that can host hydrogen appear on the surface. Heating transforms methoxy to formaldehyde, but further dehydrogenation is limited by the stability of the surface and the limited access to surface oxygen. The (root 3 x root 3)R30 degrees-reconstructed (111) surface is based on ordered surface oxygen and copper ions and vacancies, which offers a palette of adsorption and reaction sites. Already at 140 K, a mixed layer of methoxy, formaldehyde, and CHxOy is formed. Heating to room temperature leaves OCH and CHx. Thus both CH-bond breaking and CO-scission are active on this surface at low temperature. The higher ability to dehydrogenate methanol on (111) compared to (100) is explained by the multitude of adsorption sites and, in particular, the availability of surface oxygen.

Place, publisher, year, edition, pages
2017. Vol. 146, no 24, article id 244702
National Category
Physical Sciences
Research subject
Chemical Physics
Identifiers
URN: urn:nbn:se:su:diva-145191DOI: 10.1063/1.4989472ISI: 000404302600033OAI: oai:DiVA.org:su-145191DiVA, id: diva2:1128981
Available from: 2017-07-31 Created: 2017-07-31 Last updated: 2019-08-19Bibliographically approved
In thesis
1. Experimental femtosecond-laser based investigations of model catalytic surface reactions
Open this publication in new window or tab >>Experimental femtosecond-laser based investigations of model catalytic surface reactions
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In order to be able to design novel catalytic processes more efficiently, detailed understanding of the catalyst-reactant interaction and the dynamics of the microscopic reaction steps is needed. The present thesis aims to contribute to the fundamental understanding of catalyst reactant systems by means of experiments using model systems in Ultra High Vacuum (UHV). The main body of work involves femtochemistry/mass spectrometry measurements as well as sum-frequency generation (SFG) measurements, which both make use of a femtosecond laser and a UHV sample environment. The results of two experimental investigations within the field of surface science are presented.

The first paper concerns CO oxidation on ruthenium (0001) and in particular the energy transfer from substrate to adsorbates upon laser excitation. For these experiments laser-induced desorption was performed. We were able to control the branching ratios of competing mechanisms and understand the role of non-thermal electrons in the mechanisms.

The second project aims to understand the adsorption and dehydrogenation of methanol on cuprous oxide (Cu2O) which is complicated by the fact that the cuprous oxide surface reconstructs differently under different conditions. The results presented in this part were acquired using mainly X-ray Photoelectron Spectroscopy and SFG. We were able to understand the restructuring of the Cu2O surface and to show that methanol adsorbs molecularly on Cu2O(111) instead of dissociatively as a methoxy and hydrogen species as it does on Cu2O(100).

Place, publisher, year, edition, pages
Stockholm University, 2018
National Category
Atom and Molecular Physics and Optics
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-153830 (URN)
Presentation
2018-03-28, FA31, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2018-03-15 Created: 2018-03-06 Last updated: 2019-08-19Bibliographically approved
2. Experimental investigations of model catalytic surface reactions on metal and metal oxide surfaces
Open this publication in new window or tab >>Experimental investigations of model catalytic surface reactions on metal and metal oxide surfaces
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the development of renewable energies catalysis plays an important role, for example in the production of H2 gas that drives fuel cells, or in the decomposition of annoying by-products of renewable energy production. Most catalysts and catalytic processes currently used in the industry have their roots in macroscopic empirical investigations and trial and error-based optimization. In order to be able to design novel catalytic processes more efficiently, detailed understanding of the catalyst-reactant interaction and the dynamics of the microscopic reaction steps is needed. The present thesis aims to contribute to the fundamental understanding of catalyst reactant systems by means of experiments using model systems in Ultra High Vacuum. For this purpose, several surface science techniques were employed such as vibrational sum-frequency generation (SFG), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD) and femtochemistry.

In the present thesis the results of three different projects are presented. The first concerns the adsorption and decomposition of naphthalene on Ni(111). Using scanning tunnelling microscopy (STM) and density functional theory (DFT) we identify the adsorption energy and geometry of the naphthalene molecule. Using SFG and TPD we investigate the temperature dependent breakdown of the naphthalene molecule and identify geometrical changes of the adsorbate as an intermediate step in the decomposition reaction. Additionally, we observe poisoning of the surface due to graphene growth using both STM and XPS and explore the possible effect of co-adsorption with oxygen on the reaction pathway and the poisoning of the catalyst.

The second section concerns the adsorption and decomposition of ethanol and methanol on cuprous oxide (Cu2O). Using mainly XPS and SFG we show that ethanol adsorbs dissociatively on Cu2O(100) and (111) and that methanol adsorbs dissociatively on the (100) but molecularly on the (111) surface. Furthermore, we identify intermediate surface species and products of the temperature dependent dehydrogenation of both alcohols and show that the (111) surface is the more effective catalyst for decomposition.

The third section explores the physics of non-thermal excitation methods and discusses CO oxidation on ruthenium (0001) induced by an optical laser and by X-rays from a free electron laser. Based on these femtochemistry experiments we discuss in particular the energy transfer both for direct excitation and for substrate mediated excitations. We show that we were able to control the branching ratios of competing mechanisms and understand the role of non-thermal electrons in the mechanisms of optical laser excitation. Furthermore, we show that it is possible to induce CO oxidation by direct X-ray core hole excitation and can rationalize the relaxation process that leads to CO oxidation.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2019. p. 87
National Category
Other Physics Topics
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-171385 (URN)978-91-7797-706-3 (ISBN)978-91-7797-707-0 (ISBN)
Public defence
2019-09-26, FA31 sal, AlbaNova universitetscentrum, Roslagstullbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.

Available from: 2019-09-03 Created: 2019-08-13 Last updated: 2019-08-30Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full text

Search in DiVA

By author/editor
Marks, KessÖström, Henrik
By organisation
Department of Physics
In the same journal
Journal of Chemical Physics
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 25 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf