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Mitigation of CO poisoning in hydrogen fuel cell.
Kalabis, David ; Yakovlev, Yurii (advisor) ; Mališ, Jakub (referee)
This diploma thesis aims at studying a process of hydrogen fuel cell poisoning by molecules of carbon monoxide. Low loading platinum-ruthenium anode catalysts prepared by magnetron co-sputtering were studied. The chemical composition and crystallographic structure of the co-sputtered catalyst were analysed by X-ray photoelectron spectroscopy (XPS), energy- dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD). The process of CO poisoning was experimentally studied in half-cell and full-cell setups. Thin film catalysts were extensively studied using the rotating disk electrode (RDE) technique by analysing the desorption response of the underpotentially deposited hydrogen and copper as well as carbon monoxide stripping. Long-term and transient response to CO poisoning was investigated in the full cell setup (fuel cell operando mode) using galvanostatic potentiometry and impedance spectroscopy, respectively. A bifunctional mechanism of ruthenium in platinum anode catalyst was analysed. The mechanism of CO tolerance improvement either through adsorbed OH group formation and a change in electronic structure of alloys was discussed.
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Optimization of the performance of fuel cell stacks using an ultrasonic humidifier.
Vaněk, Martin ; Yakovlev, Yurii (advisor) ; Václavů, Michal (referee)
Title: Optimization of the Performance of Fuel Cell Stacks Using an Ultrasonic Humidi- fier. Author: Martin Vaněk Department: Department of Surface and Plasma Science Supervisor: Mgr. Yurii Yakovlev, Ph.D., Department of Surface and Plasma Science Abstract: This work is concerned with the optimization of the performance of PEM hydrogen fuel cell stacks, a technology that opens up new possibilities for clean energy storage and restoration. We have hand-built a PEMFC open-cathode stack of 20 cells and measured its basic characteristics such as the j-V and j-P curves as well as the dependency of the temperature of the stack on power produced by the stack for constant power of the cooling fans. We have implemented and tested the performance of a new method for water and thermal management - the humidification of air via the use of an ultrasonic water fog generator. Several tests - measuring cooling efficiency, voltage variations between different cells, and j-V and j-P curves - were performed under different temperatures and with or without humidification. Keywords: fuel cell, self humidification, open cathode, performance 1
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Candle soot as a support for proton exchange membrane fuel cell catalysts
Orság, Martin ; Khalakhan, Ivan (advisor) ; Yakovlev, Yurii (referee)
Burning of fossil fuels to power vehicles causes emissions of carbon dioxide and in consequence the global warming which, in turn, causes melting of glaciers, extinction of species and various other negative consequences. The only way to decrease the harmful emissions is a transition to emission-free energy sources such as fuel cells. A promising type of such fuel cells are hydrogen fueled proton exchange membrane fuel cells (PEMFCs). One of the main obstacles hindering their widespread commercialization is the production cost and poor durability of catalyst/support assemblies. The present thesis focuses on the possibility to use candle soot (CS) as an efficient and low-cost catalyst support and compares the power characteristics of the fuel cell utilising the candle soot support with the one utilizing a commercial catalyst support. The results show that Pt/CS assemblies exhibit comparable or even better power densities than Pt / commercial catalyst support, which makes candle soot a promising type of the support for PEMFCs catalyst.
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