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Low Platinum Content Thin Film Catalysts for Hydrogen Proton Exchange Membrane Fuel Cells
Václavů, Michal ; Matolín, Vladimír (advisor)
Novel type of catalyst for proton exchange membrane fuel cells anode is demonstrated. It is based on magnetron sputtered Pt-CeO2 a Pt-Sn-CeO2 mixed oxides. It is shown, that these materials allow to significantly decrease amount of platinum in the anode catalyst. The preparation method yields high amount of platinum in ionized form, especially Pt2+ , which is related to the high activity. Stability of these catalytic layers were investigated under conditions similar to fuel cell anode (humidified hydrogen at elevated temperature). Also interaction of hydrogen a water under UHV conditions were studied, demonstrating high stability of the Pt2+ species. In the last part of the work sputtered Pt-Co mixed catalyst were investigated to be used in the PEMFC cathode. It is demonstrated that at right conditions, the sputtered alloy catalyst improves mass activity on cathode by factor more than two.
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Model catalysts based on cerium oxide
Aulická, Marie ; Veltruská, Kateřina (advisor)
This work deals with the preparation of thin cerium oxide films on the Cu(110) single crystal. Physico-chemical properties of this system were studied by surface science techniques (XPS, UPS, ARUPS, LEED, LEEM and STM). The first part of the work concerns interaction of Cu(110) single crystal with oxygen. Condi- tions for formation of O(2x1) and Oc(6x2) oxygen reconstructions were found. Various methods of preparation of CeOx films were discussed. A novel method for continuous control of ceria stoichiometry from CeO2 to Ce2O3 through variation of oxygen vacancy concentration has been developed. Ceria facilitated oxygen spill-over was observed on copper substrate. It was found that a restructuring of copper substrate occurs at the copper-ceria interface with subsequent formation of Cu(13 13 1) facets, which support a Carpet-like ceria overlayer. Interaction of this system with platinum was studied. Finally, high temperature growth of CeOx films was studied and creation of ceria islands exposing the (110) plane was observed. 1
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Study of gas sensing properties of tungsten oxide thin films
Vojík, Jiří ; Mašek, Karel (advisor) ; Ševčíková, Klára (referee)
Purpose of this thesis is a study of gas sensing properties of pure and platinum doped tungsten oxide thin films, which are deposited on a glass substrate. Needed films were prepared by magnetron sputtering method. Chemical composition and morphology of the films were investigated by means of XPS and SEM. It was discovered that prepared films are relatively flat and homogenous. They consist of polycrystalline WO3. It emerged that platinum which is present in modified films is in form of the PtO2 and PtO oxides. During subsequent heating of the films in air, which is needed for right function of films as sensors, PtO2 partially reduced. The resistance of the films decreased after heating. Sensing properties of the films were studied at 300 řC. The platinum doped film was more sensitive to exposition of hydrogen than the pure film.
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Quantum chemical study of the electron properties of various platinum(IV) complexes and their reaction mechanisms
Šebesta, Filip ; Burda, Jaroslav (advisor) ; Straka, Michal (referee)
It has been proven that platinum complexes are active in anticancer treatment as well as several other transition metals complexes. There is an effort in recent medicine to replace cisplatin complexes by drugs with smaller side effects. This work focuses on the reaction of 5'-dGMP (2'-deoxyguanosine-5'˗monophosphate) and cGMP (cyclic 2'-deoxyguanosine- monophosphate) with a platinum complex PtIV (dach)Cl4 (dach=diaminocyclohexane). In these two cases the Pt(IV) complex is only reduced in the presence of 5'-dGMP. The first part of the explored mechanism is the substitution reaction where a coordinate-covalent bond between platinum and nitrogen N7 of guanine is formed. In the next step oxygen of phosphate group is transferred to the C8 site. Subsequently the Pt(IV) complex is reduced. The final products represent 8˗oxo˗GMP and PtII (dach)Cl2, which are active in anticancer treatment in comparison with the kineticly inert reactant. The substitution of a chloride anion ends the reaction path for cGMP forming PtIV (dach)Cl3(N7-cGMP) complex. The structures were optimized at the DFT level with B3LYP functional in the basis set 6-31G(d) and PCM/UA0 solvation model. The energy parameters were computed at the B3LYP/6˗311++G(2df,2pd) level in the IEFPCM/sUAKS solvation model. Finally, the rate constants were...
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Study of metal- tungsten oxide model system by methods of electron spectroscopy and diffraction
Polášek, Jan ; Mašek, Karel (advisor) ; Starý, Vladimír (referee)
In the present thesis structure, morphology, chemical and electronic properties of the Pt - Au/tungsten oxide model system were investigated by means of RHEED, AFM and PES. The epitaxial tungsten oxide thin films were prepared by oxidation of W(110) single-crystal surface using a RF oxygen plasma source followed by thermal annealing. Gold and Platinum were deposited "in-situ" by evaporation. Gold or platinum deposition led to the growth of oriented particles having (111) epitaxial plane as well as to the growth of polycrystalline phase. Platinum encapsulation was proved by CO adsorption observed by SRPES. Deposition of the second metal led to the formation of core - shell bimetallic clusters. Detail structure of the bimetallic system depends on the order of deposited metals and the substrate temperature. Thermal stability of the system was investigated by heating up to 600 řC.
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Use of biomarkers for assessing environmental pollution by platinum group metals
Nedvědická, Lucie ; Řezáčová, Veronika (referee) ; Komendová, Renata (advisor)
This diploma thesis in the theoretical part analyses the characteristic feature of individual platinum group elements, their toxicity, anthropogenic sources and the presence of platinum group elements in the environment of the Czech Republic. In addition, there are specified types of bioindicators focusing mainly on lichens, mosses and needles. There are described individual bioindication techniques and pre-treatment of samples for platinum metals determination in bioindicators. The subject of the experimental part is to verify the sorption efficiency and ability of platinum and palladium using the SPE method and to determine the actual platinum metal contamination in selected localities in the city of Brno. There was also the additionally subject to verify the sorption potential of selected bioindicators and determination of the environmental pollution by platinum metals using the bag technique. In the experimental part, the bioindicators of moss Pleurozium schreberi, lichen Xanthoria parietina, lichen Flavoparmelia caperata and needles Pinus nigra were used.
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LabVIEW drivers for resistor decade
Procházka, Matěj ; Čala, Martin (referee) ; Havlíková, Marie (advisor)
This bachelor's thesis deals with description resistance decade M63x and M64x from Meatest company. I described functions and possibilities of remote access. Further are described how it's developed instrument driver in LabVIEW. At the end is cited how I conduct with testing this driver.
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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.
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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.
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