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Interaction of water vapor with epitaxial layers of cerium dioxide
Morvai, Orsolya ; Šmíd, Břetislav (advisor) ; López-Roso Redondo, Jesús Rubén (referee)
This thesis investigates the interaction between water and cerium oxide, which, due to its oxygen storage activity, could be widely used in nanomedicine, catalysis, and environmental applications. Despite extensive research, a fundamental understanding of how water interacts with cerium oxide under ambient conditions has been lacking. The study utilizes scanning tunneling microscopy, near-ambient pressure X-ray photoelectron spectroscopy, and the study of water dissociation on stoichiometric CeO2(111)/Pt(111) thin films with controlled step density. The results demonstrate the identification of three adsorption species and reveal that the dissociation kinetics depend on step density. These findings provide new insights into the role of water in cerium oxide interactions under operando conditions.
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High pressure CO and methanol oxidation study over nanopowders Rare Earth Oxides and platinum thin film catalysts
Rednyk, Andrii ; Matolín, Vladimír (advisor) ; Lykhach, Yaroslava (referee) ; Šmíd, Břetislav (referee)
Title: High pressure CO and methanol oxidation study over nanopowder Rare Earth Oxides and platinum thin film catalysts Author: Mgr. Andrii Rednyk Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Vladimír Matolín, DrSc. matolin@mbox.troja.mff.cuni.cz Abstract: This doctoral thesis focuses on reactivity study of nanopowder rare earth oxides (REOs) and platinum based thin film catalysts using microreactor with high pressure reaction cell. REOs nanoparticles were prepared by new approach based on sol-gel chemistry. Magnetron sputtering technique was used for preparation of thin film samples. In the first part of the thesis CO oxidation on REOs and on Pt, PtOx thin films were performed. Among prepared REOs catalyst better activity exhibited alumina stabilized ceria, due to higher surface area. Both Pt and PtOx deposited on silicon substrate exhibited similar activity. When carbon (G-foil or C interlayer) is used as support, activity of Pt thin film decreases while PtOx preserves high activity. In the second part of the thesis steam reforming of methanol (SRM) and partial oxidation of methanol (POM) were performed on Pt thin films. It was shown that PtOx thin film exhibited superior activity compared to other samples with the same thickness. It is due to the reduction of platinum...
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Characterization of highly porous Pd-modified SnO2 sputtered thin films for H2 detection
Chundak, Mykhailo ; Veltruská, Kateřina (advisor) ; Jiříček, Petr (referee) ; Šmíd, Břetislav (referee)
Title: Characterization of highly porous Pd-modified SnO2 sputtered thin films for H2 detection Autor: Mgr. Mykhailo Chundak Department/Institute: Department of Surface and Plasma Science Supervisor of the doctoral thesis: RNDr. Kateřina Veltruská, CSc., Department of Surface and Plasma Science Abstract: This doctoral thesis contains the study of tin dioxide and Pd-doped tin dioxide samples deposited by magnetron sputtering utilizing glancing angle deposition (GLAD). Influence of the deposition parameters on the change of morphology, crystalline structure and chemical state was studied. The samples were characterized by a variety of techniques, such as: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), synchrotron radiation photoelectron spectroscopy (SRPES), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Prepared samples showed high porosity which could be controlled by deposition parameters (angle of the deposition, gas pressure and power of magnetron discharge). Highly porous SnO2 GLAD samples and Pd modified SnO2 GLAD samples were deposited on the substrates at room temperature and 300 řC. These samples were found to be polycrystalline with certain fraction of amorphous contribution, given by preparation conditions. The size of the...
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The preparation and study of catalytic system Cu(O)-CeO2 using surface analytical methods
Šmíd, Břetislav
Title: The preparation and study of catalytic system Cu(O)-CeO2 using surface analytical methods Author: Břetislav Šmíd Department: Department of Surface and Plasma Science Supervisor of the doctoral thesis: Doc. Mgr. Iva Matolínová, Dr. Abstract: This work is concerned with a study of copper/copper oxide - cerium dioxide systems and their interaction with CO and H2O molecules. Investigated samples were prepared in the form of powder catalysts and also as very well defined model inverse systems. The low temperature CO oxidation powder catalysts were studied by means of XPS, XRD, SEM, TEM and in micro-reactor system allowing the CO oxidation examination. The study of H2O adsorption and co-adsorption of H2O with CO were carried out on model inverse systems CeOx(111)/Cu(111) in ultra-high vacuum conditions using X-ray, synchrotron radiation (SRPES), resonant (RPES) photoelectron spectroscopies and LEED. It was observed on the stoichiometric surface water adsorbs molecularly at 120 K while on the reduced surface and surface of CeO2 islands on Cu(111) the H2O adsorption is partially dissociative with formation of OH groups. The increase of Ce3+ species (i.e. surface reduction) observed after H2O adsorption was explained as an electronic effect of the Ce 4f charge accumulation and Ce 5d charge depletion....
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High pressure CO and methanol oxidation study over nanopowders Rare Earth Oxides and platinum thin film catalysts
Rednyk, Andrii ; Matolín, Vladimír (advisor) ; Lykhach, Yaroslava (referee) ; Šmíd, Břetislav (referee)
Title: High pressure CO and methanol oxidation study over nanopowder Rare Earth Oxides and platinum thin film catalysts Author: Mgr. Andrii Rednyk Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Vladimír Matolín, DrSc. matolin@mbox.troja.mff.cuni.cz Abstract: This doctoral thesis focuses on reactivity study of nanopowder rare earth oxides (REOs) and platinum based thin film catalysts using microreactor with high pressure reaction cell. REOs nanoparticles were prepared by new approach based on sol-gel chemistry. Magnetron sputtering technique was used for preparation of thin film samples. In the first part of the thesis CO oxidation on REOs and on Pt, PtOx thin films were performed. Among prepared REOs catalyst better activity exhibited alumina stabilized ceria, due to higher surface area. Both Pt and PtOx deposited on silicon substrate exhibited similar activity. When carbon (G-foil or C interlayer) is used as support, activity of Pt thin film decreases while PtOx preserves high activity. In the second part of the thesis steam reforming of methanol (SRM) and partial oxidation of methanol (POM) were performed on Pt thin films. It was shown that PtOx thin film exhibited superior activity compared to other samples with the same thickness. It is due to the reduction of platinum...
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Characterization of highly porous Pd-modified SnO2 sputtered thin films for H2 detection
Chundak, Mykhailo ; Veltruská, Kateřina (advisor) ; Jiříček, Petr (referee) ; Šmíd, Břetislav (referee)
Title: Characterization of highly porous Pd-modified SnO2 sputtered thin films for H2 detection Autor: Mgr. Mykhailo Chundak Department/Institute: Department of Surface and Plasma Science Supervisor of the doctoral thesis: RNDr. Kateřina Veltruská, CSc., Department of Surface and Plasma Science Abstract: This doctoral thesis contains the study of tin dioxide and Pd-doped tin dioxide samples deposited by magnetron sputtering utilizing glancing angle deposition (GLAD). Influence of the deposition parameters on the change of morphology, crystalline structure and chemical state was studied. The samples were characterized by a variety of techniques, such as: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), synchrotron radiation photoelectron spectroscopy (SRPES), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Prepared samples showed high porosity which could be controlled by deposition parameters (angle of the deposition, gas pressure and power of magnetron discharge). Highly porous SnO2 GLAD samples and Pd modified SnO2 GLAD samples were deposited on the substrates at room temperature and 300 řC. These samples were found to be polycrystalline with certain fraction of amorphous contribution, given by preparation conditions. The size of the...
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The preparation and study of catalytic system Cu(O)-CeO2 using surface analytical methods
Šmíd, Břetislav ; Matolínová, Iva (advisor) ; Plšek, Jan (referee) ; Sofer, Zdeněk (referee)
Title: The preparation and study of catalytic system Cu(O)-CeO2 using surface analytical methods Author: Břetislav Šmíd Department: Department of Surface and Plasma Science Supervisor of the doctoral thesis: Doc. Mgr. Iva Matolínová, Dr. Abstract: This work is concerned with a study of copper/copper oxide - cerium dioxide systems and their interaction with CO and H2O molecules. Investigated samples were prepared in the form of powder catalysts and also as very well defined model inverse systems. The low temperature CO oxidation powder catalysts were studied by means of XPS, XRD, SEM, TEM and in micro-reactor system allowing the CO oxidation examination. The study of H2O adsorption and co-adsorption of H2O with CO were carried out on model inverse systems CeOx(111)/Cu(111) in ultra-high vacuum conditions using X-ray, synchrotron radiation (SRPES), resonant (RPES) photoelectron spectroscopies and LEED. It was observed on the stoichiometric surface water adsorbs molecularly at 120 K while on the reduced surface and surface of CeO2 islands on Cu(111) the H2O adsorption is partially dissociative with formation of OH groups. The increase of Ce3+ species (i.e. surface reduction) observed after H2O adsorption was explained as an electronic effect of the Ce 4f charge accumulation and Ce 5d charge depletion....
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The preparation and study of catalytic system Cu(O)-CeO2 using surface analytical methods
Šmíd, Břetislav
Title: The preparation and study of catalytic system Cu(O)-CeO2 using surface analytical methods Author: Břetislav Šmíd Department: Department of Surface and Plasma Science Supervisor of the doctoral thesis: Doc. Mgr. Iva Matolínová, Dr. Abstract: This work is concerned with a study of copper/copper oxide - cerium dioxide systems and their interaction with CO and H2O molecules. Investigated samples were prepared in the form of powder catalysts and also as very well defined model inverse systems. The low temperature CO oxidation powder catalysts were studied by means of XPS, XRD, SEM, TEM and in micro-reactor system allowing the CO oxidation examination. The study of H2O adsorption and co-adsorption of H2O with CO were carried out on model inverse systems CeOx(111)/Cu(111) in ultra-high vacuum conditions using X-ray, synchrotron radiation (SRPES), resonant (RPES) photoelectron spectroscopies and LEED. It was observed on the stoichiometric surface water adsorbs molecularly at 120 K while on the reduced surface and surface of CeO2 islands on Cu(111) the H2O adsorption is partially dissociative with formation of OH groups. The increase of Ce3+ species (i.e. surface reduction) observed after H2O adsorption was explained as an electronic effect of the Ce 4f charge accumulation and Ce 5d charge depletion....
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