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Study of 3-phase catalytic layers for polymer electrolyte fuel cells and electrolysers
Fuka, Šimon ; Matolínová, Iva (advisor) ; Khalakhan, Ivan (referee)
Title: Study of 3-phase catalytic layers for polymer electrolyte fuel cells and electrolysers Author: Šimon Fuka Department: Department of Surface and Plasma Science Supervisor: doc. Mgr. Iva Matolínová, Dr., Department of Surface and Plasma Science Abstract: The diploma thesis focuses on the study of catalytic layers for Proton Exchange Membrane Fuel Cells (PEMFC) or electrolyzers based on the mixture of platinum and cerium oxide. These layers are prepared by using magnetron sputtering, their properties are studied depending on the deposition parameters or the choice of the substrate by using SEM, AFM, XPS and then tested as an anode in the fuel cell. In addition to the morphology of the catalytic layers, it has been shown that the dispersion of very small nanoparticles of the catalyst with a size of 1-2 nm has a great effect on PEMFC performance. Most of the prepared samples gave maximal and maximal specific performance much higher than the state of art values published for Pt-CeOx system. By studying properties of the layers used as the anode catalysts, this work contributes to the understanding of PEMFC fuel cell behavior and, consequently, to its potential commercialization. Keywords: Fuel cell, cerium oxide, platinum, catalyst, magnetron sputtering
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Study of thin film catalysts for direct methanol fuel cell anode
Fusek, Lukáš ; Matolín, Vladimír (advisor) ; Nováková, Jaroslava (referee)
This thesis is focused on the study of catalyst layers for direct methanol fuel cell anode prepared by a new method using magnetron sputtering. Homemade as well as commercial supports were used. The study of properties of prepared layers was carried out in fuel cell using methods of electrochemical analysis, such as electrochemical impedance spectroscopy and cyclic voltametry for examination of conductivity, catalyst activity and resistance to poisoning by residual carbon species. Polarization curves were used to investigate power and diffusion properties. A reference cell composed of commercially-available electrodes was chosen for comparison.
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Electron microscopy study of nanostructured thin film catalysts for micro-fuel cell application
Lavková, Jaroslava ; Matolínová, Iva (advisor) ; Ruterana, Pierre (referee) ; Šubrt, Jan (referee)
Present doctoral thesis is focused on electron microscopy and spectroscopy investigation of novel metal-oxide anode catalyst for fuel cell application. Catalyst based on Pt- doped cerium oxide in form of thin layers prepared by simultaneous magnetron sputtering deposition on intermediate carbonaceous films grown on silicon substrate has been studied. The influence of catalyst support composition (a-C and CNx films), deposition time of CeOx layer and other deposition parameters, as deposition rate, composition of working atmosphere and Pt concentration on the morphology of Pt-CeOx layers has been investigated mainly by Transmission Electron Microscopy (TEM). The obtained results have shown that by suitable preparation conditions combination we are able to tune final morphology and composition of catalyst. Composition of carbonaceous films and Pt-CeOx layers was examined by complementary spectroscopy techniques - Energy Dispersive X-ray Spectroscopy (EDX), Electron Energy Loss Spectroscopy (EELS) and X-ray Photoelectron Spectroscopy (XPS). Such prepared porous structures of Pt-CeOx are of promising as anode catalytic material for real fuel cell application. Keywords: cerium oxide, platinum, fuel cell, magnetron sputtering, Transmission Electron Microscopy
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Low Platinum Content Thin Film Catalysts for Hydrogen Proton Exchange Membrane Fuel Cells
Václavů, Michal ; Matolín, Vladimír (advisor) ; Bystroň, Tomáš (referee) ; Neitzel, Armin (referee)
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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Fabrication, heat treatment and characterization of thin layer NiTi alloys
Svatuška, Michal ; Vokoun, David (advisor) ; Dlouhý, Antonín (referee) ; Novák, Pavel (referee)
NiTi alloys with nearly equiatomic chemical composition are the most studied and the most practically utilized materials from the group of the shape memory alloys (SMA). The NiTi alloy has a thermoelastic martensitic transfor- mation (MT), which its two most important properties are based on: the shape memory and the superelasticity. Thin films of NiTi alloys with thicknesses from hundreds of nm to units of µm have a wide use mainly in microelectromechanical systems (MEMS). The doctoral thesis deals with a fabrication of thin NiTi films using a deposition on silicon substrates with two techniques - the magnetron sputtering and the pulsed-laser deposition (PLD), an investigation of their mi- crostructure using x-ray diffraction, a heat treatment of amorphous NiTi films and with a verification of MT using resistometry. Furthermore, thermomechan- ical properties of a system NiTi-polyimide (NiTi-PI), namely a dependence of a curvature radius of a NiTi-PI bilayer on temperature, are studied. 1
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Preparation and Characterization of Porous Cerium Oxide/Carbon Bilayers on Silion Substrates
Dubau, Martin ; Matolínová, Iva (advisor) ; Jiříček, Petr (referee) ; Píš, Igor (referee)
This doctoral thesis concerns the preparation of porous cerium oxide/carbon bilayers on silicon substrates. In this regard, carbonaceous films in the form of amorphous carbon (a-C) and nitrogenated amorphous carbon (CNx) are considered. The influence of various process parameters of the cerium oxide deposition on the morphology of the final cerium oxide/carbon bilayer is investigated. A correlation could be found between the morphol- ogy of the bilayer and the stoichiometry of the cerium oxide film determined by means of XPS. Furthermore, a study regarding the chemical composition of the used carbonaceous films by means of various spectroscopic techniques is presented. It was found that the chemical composition of the carbonaceous films strongly depends on the deposition con- ditions of these films and influences the behaviour of these films during oxygen plasma treatment and cerium oxide deposition, respectively. 1
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Deposition of Nanocomposite Thin Films
Kratochvíl, Jiří ; Kylián, Ondřej (advisor) ; Straňák, Vítězslav (referee)
Nanocomposite thin films can find application in photovoltaics, optics, fabrication of sensors, or in biomedicine. This work investigates fabrication and characterization of thin metal-plasma polymer nanocomposite films which have direct application because of their unique optical properties (e.g. SERS - Surface-Enhanced Raman Spectroscopy) or antibacterial effects (biomedicine). We fabricated metal nanoparticles either by magnetron sputtering (island growth) or by means of gas aggregation source of nanoparticles, thereby we got nanoparticles with very different morphologies. We used silver as a material for nanoparticles because of its antibacterial effects. We incorporated these nanoparticles into sputtered Nylon and sputtered PTFE (polytetrafluoroethylene) plasma polymer matrix. These two polymers have very different chemical structure and related different surface energy. First, we compared growth of nanoparticles on substrates of sputtered Nylon and PTFE. Then we compared properties of sandwich nanocomposites polymer-Ag-polymer for both types of nanoparticles and for both matrix materials. We characterized produced thin films especially with respect to their stability in water (antibacterial films), thermal stability (sterilization by heating) and stability on the open air (storage). Finally, the tests...
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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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Investigation of defects in thin metallic films
Hruška, Petr ; Čížek, Jakub (advisor)
In the present work Mg films prepared by RF magnetron sputtering were studied. Variable energy positron annihilation spectroscopy (VEPAS) was employed for investigation of defects in the Mg films. VEPAS characterization was combined with scanning electron microscopy and X-ray diffraction in order to determine grain size, phase composition and texture. The effect of different deposition rate and deposition temperature, annealing, various substrates and film thickness on the structure and amount of defects present in the Mg films was examined. Defect studies by VEPAS showed that positrons in studied Mg films are trapped at misfit dislocations and at vacancy-like defects in grain boundaries and their density can be reduced by the deposition at elevated temperature. 1
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Studium defektů v tenkých kovových vrstvách
Hruška, Petr ; Čížek, Jakub (advisor) ; Bulíř, Jiří (referee)
In the present work Mg films prepared by RF magnetron sputtering were studied. Variable energy positron annihilation spectroscopy (VEPAS) was employed for investigation of defects in the Mg films. VEPAS characterization was combined with scanning electron microscopy and X-ray diffraction in order to determine grain size, phase composition and texture. The effect of different deposition rate and deposition temperature, annealing, various substrates and film thickness on the structure and amount of defects present in the Mg films was examined. Defect studies by VEPAS showed that positrons in studied Mg films are trapped at misfit dislocations and at vacancy-like defects in grain boundaries and their density can be reduced by the deposition at elevated temperature. 1
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