Chairperson, Graduate Committee: Robert WalkerMcIntyre, Melissa DawnJohn D. Kirtley, David M. Halat, Kyle W. Reeping and Robert A. Walker were co-authors of the article, 'In situ spectroscopic studies of carbon formation in SOFCS operating with syn-gas' in the journal 'Electrochemical Society transactions' which is contained within this thesis.Daniel M. Neuburger and Robert A. Walker were co-authors of the article, 'In operando raman spectroscopy studies of temperature dependent carbon accumulation on SOFCS operating with syn-gas' submitted to the journal 'The journal of the Electrochemical Society' which is contained within this thesis.John D. Kirtley, Anand Singh, Shamiul Islam, Josephine M. Hill and Robert A. Walker were co-authors of the article, 'Comparing in situ carbon tolerances of Sn-infiltrated and Bao-infiltrated Ni-YSZ cermet anodes in solid oxide fuel cells exposed to methane' in the journal 'The journal of physical chemistry C' which is contained within this thesis.David R. Driscoll, Martha M. Welander, Josh B. Sinrud, Stephen W.Sofie, Robert A. Walker were co-authors of the article, 'In situ formation of multifunctional ceramics : mixed ion-electron conducting properties of zirconium titanium oxides' submitted to the journal 'The journal of materials chemistry A' which is contained within this thesis.Thesis contains an article of which Melissa Dawn McIntyre is not the main author.2017-05-022017-05-022016https://scholarworks.montana.edu/handle/1/12373Solid-state electrochemical cells are efficient energy conversion devices that can be used for clean energy production or for removing air pollutants from exhaust gas emitted by combustion processes. For example, solid oxide fuel cells generate electricity with low emissions from a variety of fuel sources; solid oxide electrolysis cells produce zero-emission H2 fuel; and solid-state DeNO x cells remove NO x gases from diesel exhaust. In order to maintain high conversion efficiencies, these systems typically operate at temperatures > or = 500°C. The high operating temperatures, however, accelerate chemical and mechanical cell degradation. To improve device durability, a mechanistic understanding of the surface chemistry occurring at the cell electrodes (anode and cathode) is critical in terms of refining cell design, material selection and operation protocols. The studies presented herein utilized in operando Raman spectroscopy coupled with electrochemical measurements to directly correlate molecular/material changes with device performance in solid oxide cells under various operating conditions. Because excessive carbon accumulation with carbon-based fuels destroys anodes, the first three studies investigated strategies for mitigating carbon accumulation on Ni cermet anodes. Results from the first two studies showed that low amounts of solid carbon stabilized the electrical output and improved performance of solid oxide fuel cells operating with syn-gas (H 2/CO fuel mixture). The third study revealed that infiltrating anodes with Sn or BaO suppressed carbon accumulation with CH 4 fuel and that H 2O was the most effective reforming agent facilitating carbon removal. The last two studies explored how secondary phases formed in traditional solid oxide cell materials doped with metal oxides improve electrochemical performance. Results from the fourth study suggest that the mixed ion-electron conducting Zr 5Ti 7O 24 secondary phase can expand the electrochemically active region and increase electrochemical activity in cermet electrodes. The final study of lanthanum strontium manganite cathodes infiltrated with BaO revealed the reversible decomposition/formation of a Ba 3Mn 2O 8 secondary phase under applied potentials and proposed mechanisms for the enhanced electrocatalytic oxygen reduction associated with this compound under polarizing conditions. Collectively, these studies demonstrate that mechanistic information obtained from molecular/material specific techniques coupled with electrochemical measurements can be used to help optimize materials and operating conditions in solid-state electrochemical cells.enSolid oxide fuel cellsCatalysisRaman spectroscopyHigh temperaturesDissertationCopyright 2016 by Melissa Dawn McIntyre