Nanostructured Electrodes for Energy Conversion

  • Author / Creator
    Tucker, Ryan T.
  • 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.

  • Subjects / Keywords
  • Graduation date
    Fall 2014
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.