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Permanent link (DOI): https://doi.org/10.7939/R3GB1XP9H

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Nanostructured Electrodes for Energy Conversion Open Access

Descriptions

Other title
Subject/Keyword
vapour-liquid-solid (VLS)
nanostructured materials
nanowire
phase formation
VLS-GLAD
glancing angle deposition (GLAD)
transparent conductor
catalyst supports
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Tucker, Ryan T.
Supervisor and department
Brett, Michael (Electrical and Computer Engineering)
Examining committee member and department
Tsui, Ying (Electrical & Computer Engineering)
Thomson, Douglas (University of Manitoba)
Sit, Jeremy (Electrical and Computer Engineering)
McDermott, Mark (Chemistry)
Department
Department of Electrical and Computer Engineering
Specialization
MEMS and Nanosystems
Date accepted
2014-07-14T11:40:46Z
Graduation date
2014-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Nanoscale materials offer opportunities to employ unique physical phenomena and performance enhancement in many applications, including energy conversion. The coupling of functional materials properties and nanoscale morphologies is paramount for the successful implementation of nanostructured materials. The central theme of this thesis is the development and testing of functional nanostructured materials motivated by energy conversion applications. First, phase formation and doping are studied for metal oxide thin films comprised of arrays of high aspect ratio nanostructures fabricated by glancing angle deposition (GLAD). Second, morphology of branched nanowire structures is shown to be controllable by geometric modulation of the growth environment with a newly developed combination of vapour-liquid-solid (VLS) nanowire growth and GLAD. Phase formation in the niobium–oxygen system is systematically explored for nanopillar array thin films. The formation of different oxide and oxynitride phases via high temperature annealing is shown to be dependent on the nanopillar array porosity as well as the annealing gas type and flow. Additionally, annealing-induced morphology changes are shown to be dependent on the degree of oxygen removal during reduction. The utility of niobium oxide nanopillars as supports for platinum electrocatalysis is demonstrated, and the electrochemical performance of the combined catalyst is shown to be related to both the support morphology and phase. Doping can enhance the electrical properties of metal oxide thin films; however, doping in evaporated thin films is challenging. Niobium doping in electron beam evaporated titanium dioxide thin films is shown to be possible, and the transparent conducting properties of the niobium-doped films are evaluated. The GLAD technique is also used to demonstrate the feasibility of doped nanostructured thin films. The concept of geometric flux engineering is introduced for the growth of indium tin oxide branched nanowires via VLS-GLAD. A high degree of control over the number, size, and shape of nanowires in an array is demonstrated. Furthermore, diameter oscillation in nanowire branches is observed and a model is constructed to support the proposed mechanism of growth. The advantages and challenges for nanostructured electrodes are discussed, and further suggestions for future research are made.
Language
English
DOI
doi:10.7939/R3GB1XP9H
Rights
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 these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before 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.
Citation for previous publication
R.T. Tucker, M.D. Fleischauer, R.M. Shewchuk, A.E. Schoeller, and M.J. Brett, “Phase formation and morphology control of niobium oxide nanopillars,” Materials Science and Engineering: B 176, 626–632 (2011)A. Bonakdarpour, R.T. Tucker, M.D. Fleischauer, N.A. Beckers, M.J. Brett, and D.P. Wilkinson, “Nanopillar niobium oxides as support structures for oxygen reduction electrocatalysts,” Electrochimica Acta 85, 492–500 (2012)R.T. Tucker, N.A. Beckers, M.D. Fleischauer, and M.J. Brett, “Electron beam deposited Nb-doped TiO2 toward nanostructured transparent conductive thin films,” Thin Solid Films 525, 28–34 (2012)A.L. Beaudry, R.T. Tucker, J.M. LaForge, M.T. Taschuk, and M.J. Brett, “Indium tin oxide nanowhisker morphology control by vapour-liquid-solid glancing angle deposition,” Nanotechnology 23, 105608 (2012)R.T. Tucker, A.L. Beaudry, J.M. LaForge, M.T. Taschuk, and M.J. Brett, “A little ribbing: Flux starvation engineering for rippled indium tin oxide nanotree branches,” Applied Physics Letters 101, 193101 (2012)

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