|
| |
|
|
Electronic structure of bimetallic systems - study of gas molecule interaction
Píš, Igor ; Nehasil, Václav (advisor) ; Bartoš, Igor (referee) ; Polčík, Martin (referee)
Bimetallic Rh-V system was studied by means of surface science experimental methods. Properties of ultra-thin Rh-V layers supported by γ-Al2O3 were compared with model systems prepared by vacuum V deposition on Rh(111), Rh(110) and polycrystalline rhodium. Formation of ordered V- Rh(111)-(2×2), V-Rh(110)-(2×1) and V-Rh(110)-(1×2) subsurface alloys and their electronic and atomic structure were investigated and models of the surface reconstructions were proposed. Influence of the subsurface alloy formation on interaction with CO and O2 molecules as well as the influence of the molecule adsorption on this alloy was investigated. The bond between CO molecules and Rh-V alloy surface was weakened due to pronounced changes in surface valence band structure. Oxygen which adsorbed on the alloy surface reacted with the subsurface vanadium at elevated temperature and blocked the interaction of the metal substrate with CO molecules.
|
|
|
Study of CeOx / Rh inverse catalyst
Kettner, Miroslav ; Nehasil, Václav (advisor) ; Johánek, Viktor (referee)
Title: Study of CeOX / Rh inverse catalyst Author: Bc. Miroslav Kettner Department: Department of Surface and Plasma Science Supervisor: doc. RNDr. Václav Nehasil, Dr., Department of Surface and Plasma Science Abstract: Inverse catalysts of cerium oxide deposited on polycrystalline and monocrystalline (111) rhodium substrates were studied by means of surface science experimental methods. Growth characteristics of cerium oxide were investigated in dependence on deposition conditions and different thickness determination methods were compared. Acording to oxidizing or reducing exposition conditions changes in degree of oxidation of CeOX were observed. Further spectra analysis showed additional Ce-Rh alloy formation. Adsorption positions CO on-top and CO hollow on Rh (111) surface were differentiated by spectra fitting procedures. Oxygen absorption and reverse desorption in CeOX was confirmed. Performed experiments indicate that this process occurs through oxide-metal interface. CO oxidation reaction mechanisms at room temperature were proposed. Cerium oxide presence is necessary for reaction occurrence. Significant influence of deposited CeOX on proposed CO oxidation reaction mechanisms was proved by this way. Keywords: Rhodium, cerium oxide, alloy, inverse catalyst, CO oxidation.
|
|
|
Study of gas molecule - surface interaction
Kettner, Miroslav ; Nehasil, Václav (advisor) ; Johánek, Viktor (referee)
Title: Study of gas molecule - surface interaction Author: Miroslav Kettner Department: Department of surface and plasma science Supervisor: doc. RNDr. Václav Nehasil, Dr., Department of surface and plasma science Abstract: In this work, we examined the suitability of rhodium deposited on a plasma sprayed substrate of titanium dioxide for catalysis reactions. With X-ray photoelectron spectroscopy method, the thermal stability of TiO2 prepared with plasma spray technology on aluminum plate was tested at first. Then, rhodium was evaporated on substrate and thermal stability of the whole system Rh/TiO2 was determined. Further methods of thermal desorption spectroscopy and molecular beam were used to study adsorption and desorption of CO and reaction of CO with oxygen. It was verified that the system Rh/TiO2 ceases to adsorbing CO after heating above 620 K, also the CO reaction with oxygen exhibits considerably lower intensity after heating above 620 K. After calibrating on rhodium plate, it was determined that the intensity of CO2 creation on Rh/TiO2 is four times lower than intensity on the rhodium plate. Unprompted adsorption and desorption passivation of the system, however, seems to be the most significant problem. Therefore, the system was assessed as unsuitable for further research. Keywords: Rh, TiO2,...
|
|
|
Single Atomic Catalysts
Závodný, Adam ; Švec,, Martin (referee) ; Čechal, Jan (advisor)
Single atom catalysts are prospective class of materials, which holds promises to reach the ultimate limit of improvement in catalyst performance, selectivity, lifetime and cost reduction. The ability to efficiently capture the adsorbates at the active sites is the key prerequisite for catalytic transformation to the products. In this respect, our experimental study aims to describe the interaction of gas molecules (H2O, CO, O2 and NO) with single metal atoms (Rh, Ir, Cu) on the magnetite surface employing scanning tunneling microscopy.
|
|
|
Investments of the Automotive Industry in Precious Metals as Strategic Materials
Dvořáček, Martin ; Plíhal, Tomáš (referee) ; Rejnuš, Oldřich (advisor)
The subject of the thesis is the investment recommendations of companies operating in the automotive industry to purchase strategic raw materials, such as in particular platinum, palladium and rhodium. Thesis include a theoretical description of the topic, respectively certain forms of hedging, instruments used to hedge and brief characteristics of precious metals. Analytical and proposed section of the thesis contains specific methods, procedures and its own approach used to meet the global target of thesis.
|
|
|
Platinum group elements in waste and surface waters
Novotný, Matěj ; Řezáčová, Veronika (referee) ; Komendová, Renata (advisor)
This assignment provides a detailed description of platinum metals, their occurrence in surface and waste water and their determination options. Currently, platinum metals are widely used in the automotive industry as a part of a catalyst, as well as in medicine and jewelery. Release of these metals in pure form and the form of oxides leads to their subsequent accumulation, which directly affects fauna and flora. Due to that, the living conditions and health status of some organisms are petting worse.
|
|
|
Rhodium in the environment
Ondreášová, Klára ; Nevrlá, Jana (referee) ; Komendová, Renata (advisor)
This bachelor thesis focuses on the characteristic of rhodium, its use in the automotive industry, the occurrence in environmental compartments (air, soil, vegetation, water), accumulation and transformations. In this thesis there are also described methods of sampling for determination, the types of sample preparation, separation and preconcentration techniques necessary prior to instrumental analysis. The work also focuses on the most commonly used analytical methods of rhodium determination, which are spectrophotometric methods, AAS, ICP-AES and ICP-MS.
|
|
| |
|
| |
guest ::
