| 1. |
- Albertin, S., et al.
(författare)
-
Surface optical reflectance combined with x-ray techniques during gas-surface interactions
- 2020
-
Ingår i: Journal of Physics D. - : Institute of Physics (IOP). - 0022-3727 .- 1361-6463. ; 53:22
-
Tidskriftsartikel (refereegranskat)abstract
- High energy surface x-ray diffraction (HESXRD), x-ray reflectivity (XRR), mass spectrometry (MS) and surface optical reflectance (SOR) have been combined to simultaneously obtain sub-second information on the surface structure and morphology from a Pd(100) model catalyst during in situ oxidation at elevated temperatures and pressures resulting in Pd bulk oxide formation. The results show a strong correlation between the HESXRD and SOR signal intensities during the experiment, enabling phase determination and a time-resolved thickness estimation of the oxide by HESXRD, complemented by XRR measurements. The experiments show a remarkable sensitivity of the SOR to changes in the surface phase and morphology, in particular to the initial stages of oxidation/reduction. The data imply that SOR can detect the formation of an ultrathin PdO surface oxide layer of only 2-3 angstrom thickness.
|
|
| 2. |
- Pfaff, S., et al.
(författare)
-
Combining high-energy X-ray diffraction with Surface Optical Reflectance and Planar Laser Induced Fluorescence for operando catalyst surface characterization
- 2019
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 90:3
-
Tidskriftsartikel (refereegranskat)abstract
- We have combined three techniques, High Energy Surface X-Ray Diffraction (HESXRD), Surface Optical Reflectance, and Planar Laser Induced Fluorescence in an operando study of CO oxidation over a Pd(100) catalyst. We show that these techniques provide useful new insights such as the ability to verify that the finite region being probed by techniques such as HESXRD is representative of the sample surface as a whole. The combination is also suitable to determine when changes in gas composition or surface structure and/or morphology occur and to subsequently correlate them with high temporal resolution. In the study, we confirm previous results which show that the Pd(100) surface reaches high activity before an oxide can be detected. Furthermore, we show that the single crystal catalyst surface does not behave homogeneously, which we attribute to the surface being exposed to inhomogeneous gas conditions in mass transfer limited scenarios.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Martin, R, et al.
(författare)
-
High-Resolution X-ray Photoelectron Spectroscopy of an IrO2(110) Film on Ir(100)
- 2020
-
Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 11:17, s. 7184-7189
-
Tidskriftsartikel (refereegranskat)abstract
- High-resolution X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) were used to characterize IrO2(110) films on Ir(100) with stoichiometric as well as OH-rich terminations. Core-level Ir 4f and O 1s peaks were identified for the undercoordinated Ir and O atoms and bridging and on-top OH groups at the IrO2(110) surfaces. Peak assignments were validated by comparison of the core-level shifts determined experimentally with those computed using DFT, quantitative analysis of the concentrations of surface species, and the measured variation of the Ir 4f peak intensities with photoelectron kinetic energy. We show that exposure of the IrO2(110) surface to O2 near room temperature produces a large quantity of on-top OH groups because of reaction of background H2 with the surface. The peak assignments made in this study can serve as a foundation for future experiments designed to utilize XPS to uncover atomic-level details of the surface chemistry of IrO2(110).
|
|
