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Title
On the electrochemistry of YSZ/Ni and related model electrodes / Michael Doppler
AuthorDoppler, Michael
Thesis advisorFleig, Jürgen
PublishedWien, 2018
Descriptionix, 103 Blätter : Illustrationen, Diagramme
Institutional NoteTechnische Universität Wien, Dissertation, 2018
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Zusammenfassung in deutscher Sprache
LanguageEnglish
Document typeDissertation (PhD)
Keywords (EN)solid oxide fuel cell / Impedance spectroscopy / anodes / water splitting
URNurn:nbn:at:at-ubtuw:1-114365 Persistent Identifier (URN)
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 The work is publicly available
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On the electrochemistry of YSZ/Ni and related model electrodes [54.59 mb]
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Abstract (English)

Solid oxide fuel cells (SOFCs) are highly efficient and clean electrochemical energy converters capable of utilizing a wide variety of fuel infrastructures. Since anode performance is critical in determining SOFC lifetime, model anode electrodes, consisting of structured metal thin film electrodes on yttria stabilized zirconia (YSZ), are employed in this thesis to investigate the reaction mechanism for hydrogen oxidation in SOFC anodes. The main emphasis is put on YSZ/Ni as the standard anode material for SOFCs. Electrocatalytic properties were investigated with the polarization resistance measured by impedance spectroscopy. Measurements on an electrode series with varying TPB length (but constant area) showed that a part of the activity originated from the TPB. Using an electrode series with varying area (but constant TPB length) the unaccounted activity could clearly be attributed to a previously unknown area-related reaction pathway for hydrogen oxidation on YSZ/Ni electrodes. Variation of temperature, hydrogen and water partial pressures, and addition of hydrogen sulfide further solidified the proposed area pathway and showed the different chemical properties of the reaction pathways. Using experimental data two possible reaction mechanisms for the newly found area pathway were proposed. To further broaden the knowledge base for hydrogen reaction mechanisms on metal/ceramic electrocatalysts, experiments described above for YSZ/Ni were carried out for the following material combinations: YSZ/Pt, scandia doped zirconia/Ni, and titania/Ni. The results showed that both the metal and ceramic phase influence the electrochemical properties, showing that the metal phase does not merely act as a current collector. The results, combined with literature data, further indicate that catalytic activity of model electrodes is either controlled by the state of the electrolyte surface or by foreign phases in the TPB region.

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