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Investigation of Ir(Ox)-Ru(Oy) thin-film catalysts for oxygen evolution reaction in proton exchange membrane water electrolyzers
Hrbek, Tomáš ; Kúš, Peter (advisor)
The main focus of this work is the investigation of the anode catalysts for the Proton Exchange Membrane Water Electrolyzers (PEM-WEs). PEM-WEs play a pivotal role in the hydrogen economy concept as they allow water decomposition into oxygen and hydrogen. However, their operation requires expensive noble metal catalysts, i.e., iridium or platinum. This issue has yet to be solved to mass-produce PEM-WEs. Consequently, our main objective is to reduce the amount of iridium on the anode of PEM-WEs. We addressed this objective by two distinct approaches: morphological and chemical. With the morphological approach, plasma etching of the membrane and the magnetron sputtering of CeO2 served to increase the membrane's active surface. Hence we improved the catalysts utilization. With the chemical approach, we focused on the catalyst itself. Thus, we replaced the pure iridium catalyst with a bimetallic iridium- ruthenium one. Therefore, the activity of the catalyst was enhanced while its price got reduced. To explain and describe the catalyst's behavior, we used various electrochemical methods and surface analysis techniques. Finally, we combined both approaches to obtain one active, stable, and low-iridium-loading anode catalyst for PEM-WE.
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Preparation of one-dimensional chemical sensors of metal oxide
Sixtová, Kateřina ; Nováková, Jaroslava (advisor) ; Kúš, Peter (referee)
In this thesis, the preparation of a chemical sensor that uses a one-dimensional structure as a sensitive part is studied. First, a scanning electron microscope (SEM) was used to examine the following structures: zinc oxide nanorods, tungsten oxide nanorods, and gallium-doped zinc oxide nanorods. To verify their composition, energy-dispersive X-ray spectroscopy (EDX) was performed. Three chips were examined as well, one of which was then selected for the subsequent preparation of the nanosensor. This was achieved by lifting the structure from the substrate using a nanomanipulator integrated into the microscope with an inserted tungsten tip and placing it on a contact of the chip. To attach the nanorod to the tip, two methods were used. The first one used electrostatic attraction between the rods and the tip, while the second one was based on the deposition of platinum on the rod-tip contact using a focused ion beam (FIB) and a gas injection system (GIS).
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Morphology and physical properties of misfit layer compound "VPbS3 "
Tetalová, Kateřina ; Uhlířová, Klára (advisor) ; Kúš, Peter (referee)
The subject of this bachelor thesis is the research on the morphology and physical properties of the misfit layer compound VPbS3. The main part of the work was the study of the sample cleaved surface. We focused on chemical stability, the to- pography of the cleaved surface, the depths of cleaved artefacts and the influence of the structure of the cleaved surface on the exfoliation of the thin layers. We exfoliated the sample to two substrates - Si/SiOx/5 nm Au a Si/300 nm SiOx - to compare adhesion. We also measured the temperature dependence of the electrical resistance of the material VPbS3. Within the work were used and compared three microscope methods - optical microscopy, scanning electron microscopy and atomic force microscopy. Marginally we also focused on the growth of the crystals VPbS3 and verified their composition. From the perspective of the AFM, the sample VPbS3 is chemically stable. We managed to exfoliate a layer with a thickness of 1,9 nm to the Si/300 nm SiOx substrate and with a thickness of 0,8 nm to the Si/SiOx/5 nm Au substrate. Following the previous measurement, the electric resistivity measu- rement reports semiconducting behaviour. 1
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Thin-film catalysts for proton exchange membrane water electrolyzers and unitized regenerative fuel cells
Kúš, Peter ; Matolín, Vladimír (advisor) ; Napporn, Teko Wilhelmin (referee) ; Plecenik, Tomáš (referee)
This dissertation thesis revolves around hydrogen economy and energy-storage electrochemical systems. More specifically, it investigates the possibility of using magnetron sputtering for deposition of efficient thin-film anode catalysts with low noble metal content for proton exchange membrane water electrolyzers (PEM-WEs) and unitized regenerative fuel cells (PEM-URFCs). The motivation for this research derives from the urgent need of minimizing the price of mentioned electrochemical devices should they enter mass production. Numerous experiments were carried out, correlating the actual in-cell performance with the varying position of thin-film catalyst within the membrane electrode assembly, with the composition of high-surface support sublayer and with the chemical structure of the catalyst itself. The wide arsenal of analytical methods ranging from electrochemical impedance spectroscopy through scanning electron microscopy to photoelectron spectroscopy allowed us to describe complex phenomena behind different obtained efficiencies. Consequent systematic optimizations led to the design of novel PEM-WE anode thin-film iridium catalyst with thickness of just 50 nm, supported on optimized TiC-based sublayer which performed similarly to standard counterparts despite using just a fraction of their noble metal...
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Study of the effect of gaseous poisons on magnetron-sputtered catalyst for hydrogen fuel cell
Kalabis, David ; Vorokhta, Mykhailo (advisor) ; Kúš, Peter (referee)
Title: Study of the effect of gaseous poisons on magnetron-sputtered catalyst for hydrogen fuel cell Author: David Kalabis Department: Department of Electronics and Vacuum Physics Supervisor: Mgr. Mykhailo Vorokhta, Ph.D., Department of Surface and Plasma Science Abstract: This bachelor thesis aims at studying effects and processes occurring on the surface of different PtRu catalysts for hydrogen fuel cells in connection with gaseous poisoning by CO. For these purposes the catalytic layers containing different proportions of Pt and Ru were made on porous membranes and glassy carbon. The technology of magnetron sputtering and plasma etching were used for their preparation. The layers were studied by several techniques and the properties of the alloys with respect to CO poisoning were determined. It was shown that increasing the concentration of Ru in the PtRu catalyst leads to higher catalyst resistivity against CO poisoning. However, starting from some point the catalyst total activity in fuel cell started to decrease, indicating that there is a defined upper limit for the Ru concentration in the bimetallic catalyst equal to about 50% in the alloy. The results of this work clearly indicate the high potential of magnetron sputtered PtRu catalysts in fuel cell applications. Keywords: fuel cell, hydrogen,...
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Investigation of Ir(Ox)-Ru(Oy) thin-film catalysts for oxygen evolution reaction in proton exchange membrane water electrolyzers
Hrbek, Tomáš ; Kúš, Peter (advisor) ; Bystroň, Tomáš (referee)
The main focus of this master thesis is the investigation of the anode catalysts for the Proton Exchange Membrane Water Electrolyzers (PEM-WEs). PEM-WEs play a pivotal role in the hydrogen economy concept as they allow water decomposition into oxygen and hydrogen. However, their operation requires expensive noble metal catalysts, i.e., iridium or platinum. This issue has yet to be solved to mass-produce PEM-WEs. Consequently, our main objective is to reduce the amount of iridium on the anode of PEM-WEs. We addressed this objective by two distinct approaches: morphological and chemical. With the morphological approach, plasma etching of the membrane and the magnetron sput- tering of CeO2 served to increase the membrane's active surface. Hence we improved the catalysts utilization. With the chemical approach, we focused on the catalyst itself. Thus, we replaced the pure iridium catalyst with a bimetallic iridium-ruthenium one. Therefore, the activity of the catalyst was enhanced while its price got reduced. To ex- plain and describe the catalyst's behavior, we used various electrochemical methods and surface analysis techniques. Finally, we combined both approaches to obtain one active, stable, and low-iridium-loading anode catalyst for PEM-WE.
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Thin-film catalysts for proton exchange membrane water electrolyzers and unitized regenerative fuel cells
Kúš, Peter ; Matolín, Vladimír (advisor)
This dissertation thesis revolves around hydrogen economy and energy-storage electrochemical systems. More specifically, it investigates the possibility of using magnetron sputtering for deposition of efficient thin-film anode catalysts with low noble metal content for proton exchange membrane water electrolyzers (PEM-WEs) and unitized regenerative fuel cells (PEM-URFCs). The motivation for this research derives from the urgent need of minimizing the price of mentioned electrochemical devices should they enter mass production. Numerous experiments were carried out, correlating the actual in-cell performance with the varying position of thin-film catalyst within the membrane electrode assembly, with the composition of high-surface support sublayer and with the chemical structure of the catalyst itself. The wide arsenal of analytical methods ranging from electrochemical impedance spectroscopy through scanning electron microscopy to photoelectron spectroscopy allowed us to describe complex phenomena behind different obtained efficiencies. Consequent systematic optimizations led to the design of novel PEM-WE anode thin-film iridium catalyst with thickness of just 50 nm, supported on optimized TiC-based sublayer which performed similarly to standard counterparts despite using just a fraction of their noble metal...
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Preparation and characterization of platinum-based bimetallic catalysts for fuel cells
Supik, Lukáš ; Khalakhan, Ivan (advisor) ; Kúš, Peter (referee)
1 Abstract The main sources of energy in the world are unrenewable sources. However, its reserves should last for next few tens of years and it is necessary to substitute them with alternative sources. Fuel cells are one of the most promising alternative sources of clean energy because they convert the chemical energy of hydrogen into electrical energy with the only byproduct pure water. There exist a wide range of fuel cells and the most important type is the fuel cell with a polymer membrane because it is suitable for mobile applications. One of the main problems of fuel cells is their price. Platinum catalyst enables chemical reactions and the necessity of platinum rises its price. Nowadays, the most promising strategy for overcoming this obstacle is doping platinum with other metals. Bimetallic platinum alloys increase the catalyst's activity and simultaneously decrease its price. This thesis is focused on investigation of catalyst for fuel cell made of platinum- nickel alloy. The catalyst was prepared by magnetron sputtering technique and then its other properties were measured with respect to the amount of platinum and nickel. The goal of this thesis is to study the link between chemical composition and activity of bimetallic layers.
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