Theses and Dissertations at Montana State University (MSU)
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Item Mechanistic implications from 'in operando' optical and electrochemical studies of bio-related fuel chemistry in solid oxide fuel cells(Montana State University - Bozeman, College of Letters & Science, 2015) Kirtley, John David; Chairperson, Graduate Committee: Robert Walker; Bryan C. Eigenbrodt and Robert A. Walker were co-authors of the article, 'In situ optical studies of oxidation kinetics of NI/YSZ cermet anodes' in the journal 'ECS transactions' which is contained within this thesis.; David M. Halat, Melissa M. McIntyre, Bryan C. Eigenbrodt and Robert A. Walker were co-authors of the article, 'High temperature 'spectrochronopotentiometry': correlating electrochemical performance with in situ raman spectroscopy in solid oxide fuel cells' in the journal 'Analytical chemistry' which is contained within this thesis.; Melissa M. McIntyre, David M. Halat and Robert A. Walker were co-authors of the article, 'Insights into SOFC NI/YSZ anode degradation using in situ spectrochronopotentiometry' submitted to the journal 'ECS transactions' which is contained within this thesis.; Anand Singh, David Halat, Thomas Oswell, Josephine M. Hill and Robert A. Walker were co-authors of the article, 'In situ raman studies of carbon removal from high temperature NI-YSZ cermet anodes by gas phase reforming agents' submitted to the journal 'Journal of physical chemistry C' which is contained within this thesis.; Daniel A. Steinhurst, Jeffrey C. Owrutsky, Michael B. Pomfret and Robert A. Walker were co-authors of the article, 'In situ optical studies of methane and simulated biogas oxidation on high temperature solid oxide fuel cells' in the journal 'Physical chemistry chemical physics' which is contained within this thesis.; Daniel A. Steinhurst, Jeffrey C. Owrutsky, Michael B. Pomfret and Robert A. Walker were co-authors of the article, 'Towards a working mechanism of fuel oxidation in SOFCS: in situ optical studies of simulated biogas and methane' submitted to the journal 'Journal of physical chemistry C' which is contained within this thesis.Solid oxide fuel cells using bio-renewable fuels promise efficient, sustainable, and clean electricity production, and are becoming more attractive sources of electrical power as global consumption of non-renewables accelerates. The excellent efficiencies of solid oxide fuel cells as solid state electrochemical devices arise mainly from the direct conversion of chemical to electrical energy--through oxygen reduction at the cathode, oxide diffusion through the electrolyte, and fuel oxidation at the anode. Some of these processes possess high activation energies, requiring high operational temperatures (generally > 650 °C). These conditions can hasten deleterious carbon accumulation and anode deterioration. These high operating temperatures also pose significant challenges in directly observing chemical reactions responsible for electrochemical oxidation and materials degradation. Yet, these observations are needed to understand fundamental mechanisms responsible for these processes--an understanding necessary to improve the performance, durability and versatility of SOFCs, especially as these devices are required to operate with complex fuels and fuel mixtures. In this work, solid oxide fuel cells constructed with traditional Ni/yttrium stabilized zirconia ceramic-metallic (or cermet) anodes are studied in operando and in situ with several novel optical techniques (Raman vibrational spectroscopy, near infrared thermal imaging and fourier-transform infrared emission spectroscopy) and electrochemical measurements that provide vital insights into mechanisms surrounding bio-related fuel electrochemistry. The first study demonstrated that Ni oxidation is slower than reduction at the anode. The second study quantified electrochemically accessible anode carbon accumulation under methane fuel, while detailing deleterious mechanisms and microstructural changes that accompany cell polarization in the absence of gas phase fuels. The third study explored the kinetics of carbon removal from Ni-based anodes by CO 2, H 2O, and O 2 and detailed mechanistically why they may be different. The fourth study revealed mechanisms associated with carbon formation and current generation from biogas and methane as a function of operational condition. Collectively, these studies have begun to provide the direct, molecularly specific information necessary to empirically evaluate mechanistic descriptions of biorelated fuel electrochemistry and anode degradation.