INVESTIGATIONS OF ANNEALING EFFECTS ON STRONTIUM TITANATE ELECTRODES FOR APPLICATION AS BARE AND DYE-SENSITIZED PHOTOANODES IN PHOTOELECTROCHEMICAL CELLS

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  • March 20, 2019
Creator
  • Call, Robert
    • Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
Abstract
  • Photoelectrochemical cells (PECs) that catalyze the water-splitting reaction with solar energy have been proposed as an alternative to electrolysis of water. The electrodes for these cells must have particular qualities with regards to electrochemical stability, dielectric properties, optical bandgap, and position of band edges to create a functioning PEC. Finding a material that satisfies all of these requirements is challenge. Here we consider strontium titanate as a photoanode for these cells and attempt to modify these electrodes to have optimum properties for this application. Strontium titanate has been considered as a photoelectrode for PECs and dyesensitized solar cells because of its electrochemical stability. Its resistivity, band gap, and band edge positions are not ideal for these devices leading many investigators to attempt a wide variety of modifications to improve their performance. One common alteration is to anneal strontium titanate electrodes in a variety of atmospheres and temperatures. A significant amount of work has studied the effects of anneals on strontium titanate but a systematic study on how changes in annealing conditions effect the photoelectrochemical performance of bare and dye-sensitized strontium titanate photoelectrodes is absent from the literature. In this work the effects of annealing atmosphere and temperature on strontium titante film electrodes are evaluated in the context of their application as PEC and dyesensitized PEC photoanodes. Strontium titante films were fabricated using pulsed laser deposition. Spectroscopic techniques used for this study include x-ray diffraction, x-ray photoelectron spectroscopy, UV-Vis absorption, and spectroscopic ellipsometry. These techniques are combined with a variety of electrochemical measurements to evaluate the photoanodes. Electrochemical measurements included controlled potential techniques, transient absorption spectroscopy, Mott-Schottky analysis, and electrochemical impedance spectroscopy. A spectroelectrochemical technique for measuring density of states was attempted but did not yield significant results. A rotating ring-disk electrode setup was used to evaluate the faradaic efficiency of the electrode with the best performance.
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Advisor
  • Lopez, Rene
  • Qin, Lu-Chang
  • Washburn, Sean
  • Cecil, Gerald
  • Meyer, Thomas
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2018
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