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Electron lithography in scanning electron microscope
Haviar, Stanislav ; Lopour, Filip (referee) ; Matolín, Vladimír (advisor)
Electron beam lithography in a scanning electron microscope Tescan Miran LMH is described. Detailed parametres of preparation procedure of metal structures with characteristic dimensions below 100 nm were obtained. Additionally, a preparation of square arrays of sub 100-nm metal dots with 1 µm periode is being discussed. The lithography was performend with self-prepared resist layers (thickness < 25 nm), parameters of the spin-coating procedure are listed as well. A construction of a model single-wire sensor is described. The sensor had macroscopic gold contacts with thin (< 200 nm) tin oxide wires in between. The structures were investigated by means of scanning electron microscopy and atomic force microscopy.
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Investigation of new anode materials for methanol polymer fuel cells
Fiala, Roman ; Sofer, Zdeněk (referee) ; Matolín, Vladimír (advisor)
We investigated new types of anode catalysts for polymer membrane fule cell (PEMFC). Pt doped CeO2 thin lms were deposited by rf-magnetron sputtering on carbon nanotubes (CNTs) directly grown on GDL by using CVD. We observed considerable increase of speci c power by 1000 times and more in comparison with standard PtRu anode catalyst. For this new anode system we obtained the speci c power of 44.3 W/mg(Pt). The interaction of Pt with CeO2 layers with di erent substrates was investigated by using photoelectron spectroscopy. The results showed that platinum was in cationic state and the Pt2+/Pt4+ ratio was dependent of substrates materials. We also demonstrated that the performance of direct methanol fuel cell with Pt and PtRu catalyst can be dramatically increased simply by adding sodium hydroxide to methanol fuel. Cell voltage and power output characteristics were studied in dependence on current, temperature and concentration of sodium hydroxide. Endurance test was performed and the fuel cell exhibited stable response. Power density of 80.7 mW/cm2 was recorded for 2 M methanol/2 M sodium hydroxide fuel 30řC.
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"Ab initio" study of Cu-Ce-O interface
Szabová, Lucie ; Matolín, Vladimír (advisor) ; Chvoj, Zdeněk (referee)
"Ab initio" study of interface Cu-Ce-O Abstract: The present work is a theoretical analysis based on the numerical DFT+U simulations investigating the structural and electronic properties of Cu/CeO2 model systems, which have important applications as heterogeneous catalysts for environment protection and energy sources. We provide a detailed insight into the cohesion of the interface between metal Cu nanoparticles supported on CeO2 substrates. This issue is analyzed both in context of small supported Cu clusters as well as for the extended interface underneath Cu nanoparticles on ceria surfaces. These cases were modelled with a Cu(111)/CeO2(111) interface and with a Cu adatom adsorbed at the oxidized and reduced CeO2(111) surface, respectively. The thesis provides a direct correlation between the cohesive and electronic properties mediated by the charge transfer process. The reduction of surface cerium atoms in the presence of copper either in form of adatom, thin copper layer or a slab of copper is predicted to result from charge transferred from the metal. Since cerium reduction is suggested to play an important role into the catalytic activity of ceria-based catalysts, by predicting the reduction of cerium ions in the presence of copper it can be expected that Cu/CeO2 systems will have important...
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Investigation of CO oxidation on tin-cerium oxides by means of photoelectron spectroscopy and temperature-programmed reaction.
Václavů, Michal ; Bábor, Petr (referee) ; Matolín, Vladimír (advisor)
Metal-oxide and oxide-oxide interactions play an important role in heterogeneous catalysis. They influence electronic and crystallographic structure of catalyst surfaces, and consequently their adsorption properties. Nanosized powders of CeO2 supported tin oxide exhibit very good activity in NO reduction by CO. In order to contribute to the elucidation of the reaction mechanism we studied properties of SnO2/CeO2 by investigating the thin film model systems SnO2/CeO2/SiO2 prepared by rf-magnetron sputtering of ceria that were doped by tin oxide by means of thermal decomposition of tin acetate in air. The catalyst composition was characterized by photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The CO and NO reaction was investigated by means of a chip flow micro-reactor.
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Study of the local structure of binary surfaces by electron diffraction (XPS, LEED)
Gereová, Katarína ; Matolín, Vladimír (advisor) ; Pavluch, Jiří (referee)
Study of local structure of binary surface with usage of ultra-thin film of cerium deposited on a Pd (111) single-crystal surface is presented. X-ray photoelectron spectroscopy and diffraction (XPS, XPD), angle resolved UV photoemission spectroscopy (ARUPS) and low energy electron diffraction (LEED) was used for our investigations. LEED and X-ray excited photoemission intensities results represent a surface-geometrical structure. As well, mapping of ultra-violet photoelectron intensities as a function of emission angles is used for a band mapping and an electronic structure determination.
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