Change search
ReferencesLink to record
Permanent link

Direct link
Electronic structure and spectroscopy calculations in fuel cell catalysis
Stockholm University, Faculty of Science, Department of Physics. (Quantum Chemistry)
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents joint experimental and theoretical studies of surface phenomena at an electronic structure level in proton exchange membrane fuel cells (PEM-FC's).

The fuel cell activity can be related to the oxygen reduction taking place at the cathodic surface through the oxygen reduction reaction (ORR). Under certain conditions the dissociative adsorption of O2 becomes the rate limiting reaction step and may therefore affect the overall fuel cell activity. Using core-level spectroscopy in terms of X-ray Photoemission Spectroscopy (XPS), the O2 dissociation barrier on Pt(111) has been determined and density functional theory (DFT) calculations reproduce the estimate well, using structure models that account for lateral adsorbate-adsorbate interactions, a finding that may have implications on the approach to calculate electronic structure properties of heterogeneous surface catalysis.

Through a Brønsted-Evans-Polanyi (BEP) relation, the activation barrier for dissociation can be connected to the chemisorption energy of the atomic oxygen binding to the Pt surface. By affecting this energy, the activity of the fuel cell can be tuned; straining the Pt lattice weakens the O-Pt bond according to the Nørskov-Hammer d-band model which relates the adsorbate-substrate chemisorption energy to the position of the d-band center relative the Fermi level.

X-ray Absorption (XAS) and Emission Spectroscopy (XES) have been used together with DFT to investigate the electronic structure effect in Pt due to strain, by depositing overlayers of Pt on Cu(111). The  d-band model can to some extent be employed to describe the strain effect - but the discrepancies between the calculations and the experiments remain an open question at present.

Furthermore, the oxidation of the Pt(111) surface have been studied using XPS and XAS. DFT calculations support the experimental picture and suggest an oxidation resulting in an α-PtO2 type of surface-oxide.

Place, publisher, year, edition, pages
Henrik Öberg , 2011.
Research subject
Chemical Physics
URN: urn:nbn:se:su:diva-58807OAI: diva2:422469
Available from: 2011-06-29 Created: 2011-06-13 Last updated: 2011-06-29Bibliographically approved

Open Access in DiVA

lic_thesis_oberg(2382 kB)859 downloads
File information
File name FULLTEXT01.pdfFile size 2382 kBChecksum SHA-512
Type fulltextMimetype application/pdf

By organisation
Department of Physics

Search outside of DiVA

GoogleGoogle Scholar
Total: 859 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 63 hits
ReferencesLink to record
Permanent link

Direct link