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Permanent link (DOI): https://doi.org/10.7939/R31D7Z

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Oxidation of 2-propanol in alkaline electrolytes using platinum and ruthenium-based catalysts: prototype fuel cells and electrokinetics studies Open Access

Descriptions

Other title
Subject/Keyword
ruthenium
alkaline
2-propanol
fuel cell
platinum
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Markiewicz, Matthew Eugene Paul
Supervisor and department
Bergens, Steven H (Chemistry)
Examining committee member and department
Mar, Arthur (Chemistry)
Secanell, Marc (Mechanical Engineering)
McCreery, Richard L (Chemistry)
Wilkinson, David (Chemical and Biological Engineering)
Buriak, Jillian M (Chemistry)
Department
Department of Chemistry
Specialization

Date accepted
2011-10-04T16:53:35Z
Graduation date
2011-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Alcohols are an attractive alternative to hydrogen fuel in fuel cells. They are energy dense, easy to store, transport, and they are readily available. Alkaline fuel cells have several kinetic advantages over acidic fuel cells, but they are sensitive to carbon dioxide. The fuel most studied in direct alcohol fuel cells is methanol. The oxidation of methanol, however, produces carbon dioxide that will gradually carbonate alkaline electrolytes, degrading their performance. Investigations into the electrochemical oxidation of 2-propanol to acetone in alkaline electrolytes over platinum, platinum-ruthenium, and ruthenium catalysts were performed in three-electrode experiments. At the low anodic potentials that are required for efficient direct alcohol fuel cell, the oxidation of 2-propanol gives higher current densities than methanol over platinum. In contrast with the oxidation of methanol, which forms a stable carbon monoxide or similar surface poisoning intermediate, the oxidation of 2-propanol to acetone is believed to occur in the absence of a strongly adsorbed intermediate that hinders the reaction. Consistent with the behaviour in three-electrode experiments, prototype fuel cells operating on 2-propanol gave higher power densities than when operated on methanol, and they were also more stable. The oxidation of 2-propanol at low potentials is enhanced by surface ruthenium. Multidimensional regression of the potential-temperature-current relationship found that ruthenium reduces the activation enthalpy by an amount consistent with hydrogen bonding (9 kJ/mol). A new transition state complex where an adsorbed oxygen species on ruthenium hydrogen bonds to the alcoholic proton of an intermediate formed during the oxidation of 2-propanol is proposed to account for this stabilization. This new mode of the bifunctional mechanism is believed to be responsible for the increased rate observed during the oxidation of 2-propanol at low potentials using platinum-ruthenium catalysts. In an operating fuel cell, ruthenium was found to increase the kinetics of the reaction and reduce its onset potential. Both these factors increase the power density of prototype alkaline direct 2-propanol fuel cells when a platinum-ruthenium anode is used as the catalysts compared to when platinum is used.
Language
English
DOI
doi:10.7939/R31D7Z
Rights
License granted by Matthew Markiewicz (mem2@ualberta.ca) on 2011-10-04T16:13:45Z (GMT): Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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