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- Lissek, T, et al.
(author)
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Building Bridges through Science
- 2017
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In: Neuron. - : Elsevier BV. - 1097-4199 .- 0896-6273. ; 96:4, s. 730-735
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Journal article (peer-reviewed)
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| 5. |
- Albertin, S., et al.
(author)
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Surface optical reflectance combined with x-ray techniques during gas-surface interactions
- 2020
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In: Journal of Physics D. - : Institute of Physics (IOP). - 0022-3727 .- 1361-6463. ; 53:22
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Journal article (peer-reviewed)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.
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- Pfaff, S., et al.
(author)
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Combining high-energy X-ray diffraction with Surface Optical Reflectance and Planar Laser Induced Fluorescence for operando catalyst surface characterization
- 2019
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In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 90:3
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Journal article (peer-reviewed)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.
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- Berner, G., et al.
(author)
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LaAlO3/SrTiO3 oxide heterostructures studied by resonant inelastic x-ray scattering
- 2010
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:24, s. 241405-
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Journal article (peer-reviewed)abstract
- We report the application of resonant inelastic X-ray scattering to explore the nature of the single conducting interface in the oxide heterostructure LaAlO/sub 3//SrTiO/sub 3/. From the Ti 3d crystal-field excitations measured at the Ti L/sub 3/ resonance we not only derive information on the local geometry at the interface but are also able to follow the evolution of the sheet carrier density with the thickness of the LaAlO/sub 3/ overlayer. These findings confirm after calibration to previous hard X-ray photoelectron spectroscopy measurements that the charge density from spectroscopy exceeds the one derived from Hall-effect measurements, indicating the coexistence of itinerant /i and/ localized Ti 3d electrons at the interface. On the other hand, we observe a saturation of the charge-carrier concentration above a LaAlO/sub 3/ thickness of 6 unit cells at ~1*10/sup 14/ cm/sup -2/, well below the canonical value for ideal electronic reconstruction.
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- Linpé, W., et al.
(author)
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An electrochemical cell for 2-dimensional surface optical reflectance during anodization and cyclic voltammetry
- 2020
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In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 91:4
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Journal article (peer-reviewed)abstract
- We have developed an electrochemical cell for in situ 2-Dimensional Surface Optical Reflectance (2D-SOR) studies during anodization and cyclic voltammetry. The 2D-SOR signal was recorded from electrodes made of polycrystalline Al, Au(111), and Pt(100) single crystals. The changes can be followed at a video rate acquisition frequency of 200 Hz and demonstrate a strong contrast between oxidizing and reducing conditions. Good correlation between the 2D-SOR signal and the anodization conditions or the cyclic voltammetry current is also observed. The power of this approach is discussed, with a focus on applications in various fields of electrochemistry. The combination of 2D-SOR with other techniques, as well as its spatial resolution and sensitivity, has also been discussed.
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- Abb, Marcel J.S., et al.
(author)
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Thermal Stability of Single-Crystalline IrO2(110) Layers : Spectroscopic and Adsorption Studies
- 2020
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In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:28, s. 15324-15336
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Journal article (peer-reviewed)abstract
- The interaction of ultrathin single-crystalline IrO2(110) films with the gas phase proceeds via the coordinatively unsaturated sites (cus), in particular Ircus, the undercoordinated oxygen species on-top O (Oot) that are coordinated to Ircus, and bridging O (Obr). With the combination of different experimental techniques, such as thermal desorption spectroscopy, scanning tunneling microscopy (STM), high-resolution core-level spectroscopy (HRCLS), infrared spectroscopy, and first-principles studies employing density functional theory calculations, we are able to elucidate surface properties of single-crystalline IrO2(110). We provide spectroscopic fingerprints of the active surface sites of IrO2(110). The freshly prepared IrO2(110) surface is virtually inactive toward gas-phase molecules. The IrO2(110) surface needs to be activated by annealing to 500-600 K under ultrahigh vacuum (UHV) conditions. In the activation step, Ircus sites are liberated from on-top oxygen (Oot) and monoatomic Ir metal islands are formed on the surface, leading to the formation of a bifunctional model catalyst. Vacant Ircus sites of IrO2(110) allow for strong interaction and accommodation of molecules from the gas phase. For instance, CO can adsorb atop on Ircus and water forms a strongly bound water layer on the activated IrO2(110) surface. Single-crystalline IrO2(110) is thermally not very stable although chemically stable. Chemical reduction of IrO2(110) by extensive CO exposure at 473 K is not observed, which is in contrast to the prototypical RuO2(110) system.
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