Metal Complexes Derivatized Metal Oxides as Nanostructured Electrodes in Electrochemistry or Photoelectrochemistry  Public Deposited

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  • March 19, 2019
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  • Luo, Hanlin
    • Affiliation: College of Arts and Sciences, Department of Applied Physical Sciences, Materials Science Graduate Program
Abstract
  • This dissertation focuses on three types of metal oxide nanostructured electrodes: niobium oxides(Nb<sub>2</sub>O<sub>5</sub>), strontium oxides ( SrTiO<sub>3</sub>), and antimony-doped tin oxides (ATO) in electrochemical and/or photoelectrochemical applications. The chapter 2 and 3 discuss Nb<sub>2</sub>O<sub>5</sub> and SrTiO<sub>3</sub> respectively. Both metal oxides were investigated as alternative photoanodes to titanium dioxides (TiO2) in Dye-sensitized solar cells (DSSCs) and Dye-sensitized photoelectrosyntheis cells (DSPECs) because their conduction band are reported to be ~ 0.2-0.4 eV higher than TiO<sub>2</sub>. Systematic investigations on Nb<sub>2</sub>O<sub>5</sub> and SrTiO<sub>3</sub> in comparison to TiO2 in equivalent devices were conducted, with conduction band, energy levels of chromophore, electron transfer dynamics, current-voltage relationship, and H2 evolution or photo to current conversion efficiency discussed in the content. T-phase orthorhombic Nb<sub>2</sub>O<sub>5</sub> films have shown conduction band potential slightly positive than that for anatase TiO<sub>2</sub>. Trap state distributions, conduction band energies, and interfacial barriers appear to contribute to a slower back electron transfer rate, lower injection yield on the nsec timescale, and a lower Voc for T-phase Nb<sub>2</sub>O<sub>5</sub> compared to anatase TiO<sub>2</sub>. In chapter 3, SrTiO<sub>3</sub> photoanodes indicated slower back electron transfer than TiO<sub>2</sub> after a Znic porphyrin sensitization. They suffered from the low energy conversion efficiency due to large interfacial charge transfer resistance between conduction band of SrTiO<sub>3</sub> and electrolyte and high conduction band edge. The chapter 4 explores fabrication of 3-D mesoporous nanostructured ATO electrodes and their applications in electrochemical and photoelectrochemical catalysis. ATO nanostructured electrodes are characteristic of high interfacial area and drift electron transport. To obtain large-pore mesoporous materials, amphiphilic copolymers are chosen to as templates that unfortunately suffer from poor control of interaction with metal precursors and requirements for post annealing. Mesoporous ATO nanoelectrodes were fabricated based on ATO nanocrystals by microwave irradiation and grafted copolymers, poly (vinyl chloride)-g-poly (oxyethylene methacrylate) (PVC-g-POEM), templating. ATO nanoelectrodes indicated rapid electron transfer and proved to be suitable substrates for electrochemical catalysis after derivatized by a ruthenium water oxidation catalyst. Moreover, core-shell photoanodes, consisting of core of mesoporous conductive ATO film and shell of TiO<sub>2</sub> by atomic layer deposition (ALD), were derivatized by a ruthenium chromophore, working as a photocathode in H<sub>2</sub> evolution.
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  • In Copyright
Advisor
  • Cahoon, James
  • You, Wei
  • Warren, Scott
  • Lopez, Rene
  • Meyer, Thomas
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2014
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  • Chapel Hill, NC
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  • This item is restricted from public view for 2 years after publication.
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