Theses and Dissertations at Montana State University (MSU)
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Item Chlorine induced degradation of SOFCS operating on carbon containing fuels(Montana State University - Bozeman, College of Letters & Science, 2017) Reeping, Kyle Wyatt; Chairperson, Graduate Committee: Robert Walker; Robert A. Walker was a co-author of the article, 'In operando vibrational raman studies of chlorine contamination in solid oxide fuel cells' in the journal 'The journal of the Electrochemical Society' which is contained within this thesis.; John D. Kirtley, Jessie M. Bohn, Daniel A. Steinhurst, Jeffrey C. Owrutsky and Robert A. Walker were co-authors of the article, 'Chlorine-induced degradation in solid oxide fuel cells identified by optical methods' in the journal 'The journal of physical chemistry C' which is contained within this thesis.; Jessie, M. Bohn and Robert A. Walker were co-authors of the article, 'Chlorine-induced degradation in SOFCS operating with biogas' in the journal 'Sustainable energy and fuels' which is contained within this thesis.; Jessie, M. Bohn and Robert A. Walker were co-authors of the article, 'The palliative effect of H 2 on SOFCS operating on contaminated carbon containing fuels' submitted to the journal 'The journal of power sources' which is contained within this thesis.Chlorine present in green and synthetic fuels such as biogas and syngas can accelerate degradation of solid oxide fuel cell (SOFC) nickel-based anodes. Chlorine contamination has been studied in SOFCs where H 2 was the primary fuel but little attention has focused on deleterious, cooperative effects that result from Cl-contamination in predominantly carbon-containing fuels. Experiments described in this work examine degradation mechanisms in SOFCs with Ni-YSZ cermet anodes operating with a biogas surrogate and exposed to 110 ppm Cl (delivered either as CH 3Cl or HCl). Operando Raman spectroscopy is used to directly observe the the anode's catalytic activity as evidenced by observable carbon accumulation, and electrochemical impedance and voltammetry measurements report on overall cell performance. Studies performed at 650 °C and 700 °C show that Cl suppresses carbon accumulation and causes slow but steady cell degradation. Prolonged exposure to Cl results in and irreversible device failure. These results differ markedly from recent reports of Cl contamination in SOFCs operating independently with H 2 and CH 4.Item Biochemical characterization of the [FeFe]-hydrogenase maturation protein HydE and identification of the substrate(Montana State University - Bozeman, College of Letters & Science, 2011) Boswell, Nicholas William Bradford; Chairperson, Graduate Committee: Joan B. BroderickHydrogenases catalyze the reversible reduction of protons using complex metal clusters with unusual ligands. The catalytic center of the [FeFe]-hydrogenases is called the H-cluster, and is characterized by a [4Fe-4S] cluster connected via a cysteine thiolate to a 2Fe subcluster coordinated by carbon monoxide and cyanide ligands as well as a bridging dithiolate. Assembly of the H-cluster is carried out by three hydrogenase maturation proteins: HydE, HydF, and HydG. HydF is a GTPase and has been implicated to serve as a scaffold for assembly of the 2Fe subcluster of the H-cluster. HydE and HydG are radical S-adenosylmethionine (SAM) enzymes and thus are thought to utilize reductive cleavage of SAM to initiate radical chemistry. HydG has been shown to catalyze the formation of the carbon monoxide and cyanide ligands of the H-cluster utilizing tyrosine as a substrate. HydE, therefore, has been proposed to be responsible for biosynthesis of the dithiolate ligand of the H-cluster. The aim of this study was to biochemically characterize active, Fe-S reconstituted HydE and to identify the substrate of this radical SAM enzyme. Questions to be studied also included studying the role of HydE in H-cluster maturation. This study used protein purified from recombinant E. coli. The purified protein was chemically reconstituted with iron and sulfide, and used for spectroscopic characterization and HPLC based activity assays. Colorimetric assays were also used for protein characterization and to test for the consumption of substrate. The results indicate that cysteine is likely the substrate of HydE. Activity assays show that HydE- catalyzed SAM cleavage is stimulated in the presence of cysteine, and HydF purified from different genetic backgrounds shows a spectroscopic shift in the lambda max when both HydE and cysteine are present during growth. Spectroscopic characterization confirms that HydE is an Fe-S containing radical SAM enzyme and that cysteine may be a substrate during [FeFe]-hydrogenase H-cluster maturation.