| 1. |
- Zhou, Jianfeng, et al.
(författare)
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Combining Planar Laser-Induced Fluorescence with Stagnation Point Flows for Small Single-Crystal Model Catalysts: CO Oxidation on a Pd(100)
- 2019
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- A stagnation flow reactor has been designed and characterized for both experimental and modeling studies of single-crystal model catalysts in heterogeneous catalysis. Using CO oxidation over a Pd(100) single crystal as a showcase, we have employed planar laser-induced fluorescence (PLIF) to visualize the CO2 distribution over the catalyst under reaction conditions and subsequently used the 2D spatially resolved gas phase data to characterize the stagnation flow reactor. From a comparison of the experimental data and the stagnation flow model, it was found that characteristic stagnation flow can be achieved with the reactor. Furthermore, the combined stagnation flow/PLIF/modeling approach makes it possible to estimate the turnover frequency (TOF) of the catalytic surface from the measured CO2 concentration profiles above the surface and to predict the CO2, CO and O2 concentrations at the surface under reaction conditions.
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| 2. |
- Abb, Marcel J.S., et al.
(författare)
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Thermal Stability of Single-Crystalline IrO2(110) Layers : Spectroscopic and Adsorption Studies
- 2020
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:28, s. 15324-15336
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Bao, Yupan, et al.
(författare)
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Single-shot 3D imaging of hydroxyl radicals in the vicinity of a gliding arc discharge
- 2021
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Ingår i: Plasma Sources Science and Technology. - : IOP Publishing. - 0963-0252 .- 1361-6595. ; 30:4
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Tidskriftsartikel (refereegranskat)abstract
- Chemical processing by plasma is utilized in many applications. Plasma-related studies, however, are challenging to carry out due to plasmas' transient and unpredictable behavior, excessive luminosity emission, 3D complexity and aggressive chemistry and physiochemical interactions that are easily affected by external probing. Laser-induced fluorescence is a robust technique for non-intrusive investigations of plasma-produced species. The hydroxyl radical (OH) is an interesting molecule to target, as it is easily produced by plasmas in humid air. In this letter, we present 3D distributions of ground state OH radicals in the vicinity of a glow-type gliding arc plasma. Such radical distributions, with minimal plasma emission, are captured instantaneously in one single camera acquisition by combining structured laser illumination and a lock-in based imaging analysis method called FRAME. The orientation of the plasma discharge can be reconstructed from the 3D data matrix, which can then be used to calculate 2D distributions of ground state OH radicals in a plane perpendicular to the orientation of the plasma channel. Our results indicate that OH distributions around a gliding arc are strongly affected by gas dynamics. We believe that the ability to instantaneously capture 3D transient molecular distributions in a plasma discharge, with minimal plasma emission interference, will have a strong impact on the plasma community for in-situ investigations of plasma-induced chemistry and physics.
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| 4. |
- Blomberg, Sara, et al.
(författare)
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Combining synchrotron light with laser technology in catalysis research
- 2018
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Ingår i: Journal of Synchrotron Radiation. - 1600-5775 .- 0909-0495. ; 25:5, s. 1389-1394
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Tidskriftsartikel (refereegranskat)abstract
- High-energy surface X-ray diffraction (HESXRD) provides surface structural information with high temporal resolution, facilitating the understanding of the surface dynamics and structure of the active phase of catalytic surfaces. The surface structure detected during the reaction is sensitive to the composition of the gas phase close to the catalyst surface, and the catalytic activity of the sample itself may affect the surface structure, which in turn may complicate the assignment of the active phase. For this reason, planar laser-induced fluorescence (PLIF) and HESXRD have been combined during the oxidation of CO over a Pd(100) crystal. PLIF complements the structural studies with an instantaneous two-dimensional image of the CO2 gas phase in the vicinity of the active model catalyst. Here the combined HESXRD and PLIF operandomeasurements of CO oxidation over Pd(100) are presented, allowing for an improved assignment of the correlation between sample structure and the CO2distribution above the sample surface with sub-second time resolution.
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| 5. |
- Garcia-Martinez, Fernando, et al.
(författare)
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Catalytic oxidation of CO on a curved Pt(111) surface : simultaneous ignition at all facets through a transient CO-O complex.
- 2020
-
Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 59:45, s. 20037-20043
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic oxidation of carbon monoxide (CO) on transition metals, such as platinum (Pt), is commonly viewed as a sharp transition from the CO-inhibited surface to the active metal, covered with oxygen (O). However, we find that minor amounts of O are present in the CO-poisoned layer that explain why, surprisingly, CO desorbs at stepped and flat Pt crystal planes at once, regardless of the reaction conditions. Using near-ambient pressure X-ray photoemission and a curved Pt(111) crystal we probe the chemical composition at surfaces with variable step density during the CO oxidation reaction. The systematic analysis of carbon and oxygen core levels across the curved crystal reveals that, right before light-off, subsurface O builds up within (111) terraces. This is key to trigger the simultaneous ignition of the catalytic reaction at different Pt surfaces, as indicated by ab-initio theory: a CO-Pt-O complex is formed that equals the CO chemisorption energy at terraces and steps, leading to the abrupt desorption of poisoning CO from all crystal facets at the same temperature.
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| 6. |
- Garcia-Martinez, Fernando, et al.
(författare)
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Structure Matters: Asymmetric CO Oxidation at Rh Steps with Different Atomic Packing
- 2022
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 144:33, s. 15363-15371
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Tidskriftsartikel (refereegranskat)abstract
- Curved crystals are a simple but powerful approach to bridge the gap between single crystal surfaces and nanoparticle catalysts, by allowing a rational assessment of the role of active step sites in gas-surface reactions. Using a curved Rh(111) crystal, here, we investigate the effect of A-type (square geometry) and B-type (triangular geometry) atomic packing of steps on the catalytic CO oxidation on Rh at millibar pressures. Imaging the crystal during reaction ignition with laser-induced CO2 fluorescence demonstrates a two-step process, where B-steps ignite at lower temperature than A-steps. Such fundamental dissimilarity is explained in ambient pressure X-ray photoemission (AP-XPS) experiments, which reveal partial CO desorption and oxygen buildup only at B-steps. AP-XPS also proves that A-B step asymmetries extend to the active stage: at A-steps, low-active O-Rh-O trilayers buildup immediately after ignition, while highly active chemisorbed O is the dominant species on B-type steps. We conclude that B-steps are more efficient than A-steps for the CO oxidation.
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| 7. |
- Gericke, Sabrina M., et al.
(författare)
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Effect of Different In 2 O 3 (111) Surface Terminations on CO 2 Adsorption
- 2023
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Ingår i: ACS Applied Materials & Interfaces. - 1944-8252 .- 1944-8244. ; 15:38, s. 45367-45377
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Tidskriftsartikel (refereegranskat)abstract
- In2O3-based catalysts have shown high activity and selectivity for CO2 hydrogenation to methanol; however, the origin of the high performance of In2O3 is still unclear. To elucidate the initial steps of CO2 hydrogenation over In2O3, we have combined X-ray photoelectron spectroscopy and density functional theory calculations to study the adsorption of CO2 on the In2O3(111) crystalline surface with different terminations, namely, the stoichiometric, reduced, and hydroxylated surface. The combined approach confirms that the reduction of the surface results in the formation of In adatoms and that water dissociates on the surface at room temperature. A comparison of the experimental spectra and the computed core-level shifts (using methanol and formic acid as benchmark molecules) suggests that CO2 adsorbs as a carbonate on all three surface terminations. We find that the adsorption of CO2 is hindered by hydroxyl groups on the hydroxylated surface.
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| 8. |
- Gericke, Sabrina M., et al.
(författare)
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Effect of Different In2O3(111) Surface Terminations on CO2 Adsorption
- 2023
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 15:38, s. 45367-45377
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Tidskriftsartikel (refereegranskat)abstract
- In2O3-based catalysts have shown high activity and selectivity for CO2 hydrogenation to methanol; however, the origin of the high performance of In2O3 is still unclear. To elucidate the initial steps of CO2 hydrogenation over In2O3, we have combined X-ray photoelectron spectroscopy and density functional theory calculations to study the adsorption of CO2 on the In2O3(111) crystalline surface with different terminations, namely, the stoichiometric, reduced, and hydroxylated surface. The combined approach confirms that the reduction of the surface results in the formation of In adatoms and that water dissociates on the surface at room temperature. A comparison of the experimental spectra and the computed core-level shifts (using methanol and formic acid as benchmark molecules) suggests that CO2 adsorbs as a carbonate on all three surface terminations. We find that the adsorption of CO2 is hindered by hydroxyl groups on the hydroxylated surface.
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| 9. |
- Harlow, Gary S., et al.
(författare)
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HAT : a high-energy surface X-ray diffraction analysis toolkit
- 2023
-
Ingår i: Journal of Applied Crystallography. - 0021-8898. ; 56, s. 312-321
-
Tidskriftsartikel (refereegranskat)abstract
- This work introduces the high-energy surface X-ray diffraction analysis toolkit (HAT), an open-source cross-platform software package written in Python to allow the extraction and processing of high-energy surface X-ray diffraction (HESXRD) data sets. Thousands of large-area detector images are collected in a single HESXRD scan, corresponding to billions of pixels and hence reciprocal space positions. HAT is an optimized reciprocal space binner that implements a graphical user interface to allow the easy and interactive exploration of HESXRD data sets. Regions of reciprocal space can be selected with movable and resizable masks in multiple views and are projected onto different axes to allow the creation of reciprocal space maps and the extraction of crystal truncation rods. Current and future versions of HAT can be downloaded and used free of charge.
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| 10. |
- Larsson, Alfred, et al.
(författare)
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Operando Surface Optical Reflectance Microscopy Study of Corrosion Film Growth on a Ni-Cr-Mo Alloy During Anodic Polarization
- 2023
-
Ingår i: Journal of Physical Chemistry C. - 1932-7447. ; 127:44, s. 21871-21877
-
Tidskriftsartikel (refereegranskat)abstract
- The solid-liquid interface, where corrosion reactions occur, is notoriously difficult to study in operando conditions. Few experimental techniques can provide surface sensitivity and spatial and temporal resolution and are compatible with liquid environments. 2-Dimensional surface optical reflectance (2D-SOR) is an emerging optical technique providing microscopic information with high temporal resolution. It complements methods such as ambient pressure X-ray photoelectron spectroscopy or inductively coupled plasma-mass spectrometry, which provides valuable chemical information from the surface and the dissolving species but lacks spatial resolution. Here, we show how 2D-SOR can be used to measure the formation and growth of corrosion products in operando through oscillations in the reflected signal caused by constructive and destructive interference of the light in the film of growing corrosion products. The total thickness of the corrosion product film obtained with 2D-SOR agrees well with that measured using scanning electron microscopy ex situ. 2D-SOR has proved to be an excellent and valuable tool for monitoring the corrosion process with spatial resolution in operating conditions.
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| 11. |
- Larsson, Alfred, et al.
(författare)
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Operando Surface Optical Reflectance Microscopy Study of Corrosion Film Growth on a Ni-Cr-Mo Alloy During Anodic Polarization
- 2023
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 127:44, s. 21871-21877
-
Tidskriftsartikel (refereegranskat)abstract
- The solid-liquid interface, where corrosion reactions occur, is notoriously difficult to study in operando conditions. Few experimental techniques can provide surface sensitivity and spatial and temporal resolution and are compatible with liquid environments. 2-Dimensional surface optical reflectance (2D-SOR) is an emerging optical technique providing microscopic information with high temporal resolution. It complements methods such as ambient pressure X-ray photoelectron spectroscopy or inductively coupled plasma-mass spectrometry, which provides valuable chemical information from the surface and the dissolving species but lacks spatial resolution. Here, we show how 2D-SOR can be used to measure the formation and growth of corrosion products in operando through oscillations in the reflected signal caused by constructive and destructive interference of the light in the film of growing corrosion products. The total thickness of the corrosion product film obtained with 2D-SOR agrees well with that measured using scanning electron microscopy ex situ. 2D-SOR has proved to be an excellent and valuable tool for monitoring the corrosion process with spatial resolution in operating conditions.
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| 12. |
- Linpé, Weronica, et al.
(författare)
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Revisiting Optical Reflectance from Au(111) Electrode Surfaces with Combined High-Energy Surface X-ray Diffraction
- 2021
-
Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 168:9
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Tidskriftsartikel (refereegranskat)abstract
- We have combined high-energy surface X-ray diffraction (HESXRD) with 2D surface optical reflectance (2D-SOR) to perform in situ electrochemical measurements of a Au(111) electrode in 0.1 M HClO4 electrolyte. We show that electrochemically induced changes to Au(111) surface during cyclic voltammetry can be simultaneously observed with 2D-SOR and HESXRD. We discuss how small one atom high 1x1 islands, accommodating excess atoms after the lifting of the surface reconstruction, can lead to discrepancies between the two techniques. The use of HESXRD allows us to simultaneously detect parts of the truncation rods from the (1 x 1) surface termination and the p x root 3 electrochemically induced surface reconstruction, during cyclic voltammetry. The presence of reconstruction phenomena is shown to not depend on having an ideally prepared surface and can in fact be observed after going to very oxidizing potentials. 2D-SOR can also detect the oxidation of the Au surface, however no oxide peaks are detected in the HESXRD signal, which is evidence that any Au oxide is X-ray amorphous.
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| 13. |
- Mehar, Vikram, et al.
(författare)
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Formation of Epitaxial PdO(100) During the Oxidation of Pd(100)
- 2023
-
Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 14:38, s. 8493-8499
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The catalytic oxidation of CO and CH4 can be strongly influenced by the structures of oxide phases that form on metallic catalysts during reaction. Here, we show that an epitaxial PdO(100) structure forms at temperatures above 600 K during the oxidation of Pd(100) by gaseous O atoms as well as exposure to O2-rich mixtures at millibar partial pressures. The oxidation of Pd(100) by gaseous O atoms preferentially generates an epitaxial, multilayer PdO(101) structure at 500 K, but initiating Pd(100) oxidation above 600 K causes an epitaxial PdO(100) structure to grow concurrently with PdO(101) and produces a thicker and rougher oxide. We present evidence that this change in the oxidation behavior is caused by a temperature-induced change in the stability of small PdO domains that initiate oxidation. Our discovery of the epitaxial PdO(100) structure may be significant for developing relationships among oxide structure, catalytic activity, and reaction conditions for applications of oxidation catalysis.
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| 14. |
- Pfaff, Sebastian, et al.
(författare)
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A Polycrystalline Pd Surface Studied by Two-Dimensional Surface Optical Reflectance during CO Oxidation : Bridging the Materials Gap
-
Ingår i: ACS applied materials & interfaces. - 1944-8244.
-
Tidskriftsartikel (refereegranskat)abstract
- Industrial catalysts are complex materials systems operating in harsh environments. The active parts of the catalysts are nanoparticles that expose different facets with different surface orientations at which the catalytic reactions occur. However, these facets are close to impossible to study in detail under industrially relevant operating conditions. Instead, simpler model systems, such as single crystals with a well-defined surface orientation, have been successfully used to study gas-surface interactions such as adsorption and desorption, surface oxidation, and oxidation/reduction reactions. To more closely mimic the many facets exhibited by nanoparticles and thereby close the so-called materials gap, there has also been a recent move toward using polycrystalline surfaces and curved crystals. However, these studies are limited either by the pressure or spatial resolution at realistic pressures or by the number of surfaces studied simultaneously. In this work, we demonstrate the use of reflectance microscopy to study a vast number of catalytically active surfaces simultaneously under realistic and identical reaction conditions. As a proof of concept, we have conducted an operando experiment to study CO oxidation over a Pd polycrystal, where the polycrystalline surface acts as a collection of many single-crystal surfaces. Finally, we visualized the resulting data by plotting the reflectivity as a function of surface orientation. We think the techniques and visualization methods introduced in this work will be key toward bridging the materials gap in catalysis.
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| 15. |
- Pfaff, Sebastian
(författare)
-
On the Chemical Romance Between Gas and Surface, and how to Illuminate it
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An increasing number of catalysis experiments are conducted at higher pressures to bridge the pressure gap. This means that we need to measure not only the sample surface but also the gas phase around the sample with spatial resolution. This thesis treats the development and applications of two optical techniques that can be used to image the surface of a model catalyst together with the surrounding gas: planar laser-induced fluorescence (PLIF) and 2D-surface optical reflectance (2D-SOR). The strengths and weaknesses of the techniques are discussed. Examples are used to show how the techniques can be applied to study active model catalysts \textit{in situ} under ambient pressure conditions. PLIF is used to image the CO and CO₂ concentrations around various Pd model catalysts during the CO oxidation reaction. 2D-SOR is used to show the surface oxidation process during the same reaction. We show how PLIF and 2D-SOR can be combined with additional techniques, primarily high-energy surface X-ray diffraction (HESXRD), thermography, mass spectrometry (MS) and polarisation modulation infrared reflection absorption spectroscopy (PMIRRAS).Finally, we show how PLIF and 2D-SOR can be used to bridge the so-called materials gap by taking advantage of the spatial resolution of the techniques to study polycrystalline samples. These samples, which exhibit a plethora of surface structures, can be seen as a step towards more industry-like samples.
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| 16. |
- Pfaff, Sebastian, et al.
(författare)
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Operando Reflectance Microscopy on Polycrystalline Surfaces in Thermal Catalysis, Electrocatalysis, and Corrosion
- 2021
-
Ingår i: ACS applied materials & interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:16, s. 19530-19540
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a microscope with a spatial resolution of 5 μm, which can be used to image the two-dimensional surface optical reflectance (2D-SOR) of polycrystalline samples in operando conditions. Within the field of surface science, operando tools that give information about the surface structure or chemistry of a sample under realistic experimental conditions have proven to be very valuable to understand the intrinsic reaction mechanisms in thermal catalysis, electrocatalysis, and corrosion science. To study heterogeneous surfaces in situ, the experimental technique must both have spatial resolution and be able to probe through gas or electrolyte. Traditional electron-based surface science techniques are difficult to use under high gas pressure conditions or in an electrolyte due to the short mean free path of electrons. Since it uses visible light, SOR can easily be used under high gas pressure conditions and in the presence of an electrolyte. In this work, we use SOR in combination with a light microscope to gain information about the surface under realistic experimental conditions. We demonstrate this by studying the different grains of three polycrystalline samples: Pd during CO oxidation, Au in electrocatalysis, and duplex stainless steel in corrosion. Optical light-based techniques such as SOR could prove to be a good alternative or addition to more complicated techniques in improving our understanding of complex polycrystalline surfaces with operando measurements.
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| 17. |
- Pfaff, Sebastian, et al.
(författare)
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Temperature characterization of an operando flow reactor for heterogeneous catalysis
- 2019
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 52:32
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present several methods to determine the temperature of a catalyst sample, as well as the gas surrounding it, in a typical flow reactor used for operando research on heterogeneous catalysis. To determine the sample temperature, we present an approach using calibrated IR-camera imagery, as well as thermographic phosphors. For the gas temperature, we present methods to extract temperature information from Planar Laser Induced Fluorescence (PLIF) measurements, one of which can be used during operando studies with an active catalyst in place.
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| 18. |
- Pfaff, Sebastian, et al.
(författare)
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Visualizing the Gas Diffusion Induced Ignition of a Catalytic Reaction
- 2022
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; :12, s. 6589-6595
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Tidskriftsartikel (refereegranskat)abstract
- Many surface science experiments within heterogeneous catalysis are now conducted in realistic conditions at higher pressures. At these pressures, localized gas conditions will form throughout the reactor. Understanding these gas conditions and their interaction with the catalyst surface at relevant time scales and with spatial resolution is important. To address this issue, we use a combination of techniques that can resolve the gas and surface composition with enough temporal and spatial resolution to show even very rapid gas–surface interactions. Planar laser-induced fluorescence is used to monitor the gas phase, thermography visualizes the surface temperature, and 2D-surface optical reflectance measurements show oxide growth. By combining these techniques in an operando experiment, we demonstrate that the spatial evolution of the catalytic ignition of CO oxidation over Pd(100) at higher pressures is driven by localized gas conditions, emphasizing the need for 2D gas-phase measurements when studying model catalysts in high-pressure conditions.
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| 19. |
- Rämisch, Lisa, et al.
(författare)
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Ambient pressure operando catalytic characterization by combining PM-IRRAS with planar laser-induced fluorescence and surface optical reflectance imaging
- 2024
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Ingår i: Catalysis Today. - 0920-5861. ; 427
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Tidskriftsartikel (refereegranskat)abstract
- We present a combination of optical operando techniques that allow us to bridge the pressure gap in heterogeneous catalysis. By combining Polarization Modulated - InfraRed Reflection Absorption Spectroscopy (PM-IRRAS) with two dimensional-Surface Optical Reflectance (2D-SOR) and Planar Laser Induced Fluorescence (PLIF), we can simultaneously measure the adsorbed species on the catalyst surface, monitor the surface oxide formation across the catalyst surface and image the gas phase right above the catalyst surface, respectively. In a single measurement, we are able to follow heterogeneous catalytic reactions temporally- and spatially resolved with all three optical techniques, which are additionally supported by Mass Spectrometry (MS). To validate the experimental setup, we perform two experiments studying CO oxidation on Pd(100) at 150 mbar and 910 mbar by ramping the sample temperature. PM-IRRAS and 2D-SOR reveal that the formation of well-defined ultrathin surface oxide coincides with the disappearance of CO adsorption on the surface. At the same time, PLIF and MS confirm the simultaneous transition into a mass-transfer-limited (MTL) regime. A difference between 150 and 910 mbar can be seen in the light-off temperature caused by different partial pressures of CO and in the spatial distribution of the gas cloud across the surface in space caused by gas diffusion. This emphasizes the need for spatially-resolved gas phase diagnostics in heterogeneous catalysis. The combination of all techniques aids our understanding of the gas-surface interaction.
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| 20. |
- Rämisch, Lisa, et al.
(författare)
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Combining PM-IRRAS with optical imaging techniques for operando studies of CO oxidation
- 2021
-
Ingår i: CLEO : QELS_Fundamental Science, CLEO: QELS 2021 - QELS_Fundamental Science, CLEO: QELS 2021. - 9781557528209
-
Konferensbidrag (refereegranskat)abstract
- To bridge the pressure gap in heterogeneous catalysis and maximize the gain of operando information, we have combined PM-IRRAS with the imaging techniques SOR and PLIF and measured CO oxidation on a Pd(100) crystal.
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| 21. |
- Rämisch, Lisa, et al.
(författare)
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Infrared surface spectroscopy and surface optical reflectance for operando catalyst surface characterization
- 2022
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 578
-
Tidskriftsartikel (refereegranskat)abstract
- Using a new sample environment, the two operando surface diagnostic techniques two-dimensional surface optical reflection (2D-SOR) and polarization-modulated infrared reflection–absorption spectroscopy (PM-IRRAS) have been combined with mass spectrometry (MS) to characterize a catalytic reaction. With both techniques integrated in a custom-built setup, we can correlate molecular information of the adsorbed surface species from PM-IRRAS with information about oxide formation on the sample from 2D-SOR. The new setup was evaluated by performing CO oxidation over a Palladium single crystal Pd(1 0 0) surface. The results reveal that the macroscopic and the microscopic molecular behavior correlate well. When the CO adsorption peak disappears in the PM-IRRAS spectrum, the formation of a well-defined ultra-thin surface oxide is observed in the 2D-SOR trend. We discuss the benefits and limitations of the two techniques as well as their potential for further studies of catalytic reactions at both gas–solid and liquid–solid interfaces.
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| 22. |
- Zhou, Jianfeng, et al.
(författare)
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A convenient setup for laser-induced fluorescence imaging of both CO and CO2 during catalytic CO oxidation
- 2017
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Ingår i: Applied Physics B: Lasers and Optics. - : Springer Science and Business Media LLC. - 0946-2171. ; 123:3
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Tidskriftsartikel (refereegranskat)abstract
- In-situ knowledge of the gas composition close to a catalyst is essential for a better understanding of the gas–surface interaction. With planar laser-induced fluorescence (PLIF), the gas distribution around an operating catalyst can be visualized with high spatial and temporal resolution, in a non-intrusive manner. We report on a convenient setup using a nanosecond YAG-Dye laser system together with a broadband mid-infrared optical parametric oscillator (OPO) for imaging both CO and CO2 over a Pd(100) catalyst during catalytic CO oxidation, compare it to previously used systems, and show examples of its capabilities.
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