Titania Thin Films and Multijunction Solar Cell in an H-type Photoreactor for Photocatalytic Water Splitting Reaction to Produce Hydrogen
Date Issued
2012
Date
2012
Author(s)
Huang, Chao-Wei
Abstract
Nowadays, humans face two crises: energy shortage and global warming. In order to meet the energy demand, it is imperative for us to search for an alternative energy. Solar energy in the form of hydrogen is the ultimate energy that could overcome these difficulties. Hydrogen not only is a medium for storing solar energy, but also a clean and recyclable energy source. In this study, titania thin films and multijunction solar cell were used as the photocatalysts or photoelectrodes to produce hydrogen via photocatalytic water splitting reaction in an H-type reactor. Titania is one of the popular photocatalyst materials. Under the irradiation of light with energy greater than bandgap, the photocatalyst would generate electron-and-hole pairs. These electrons and holes will reduce and oxidize water to form hydrogen and oxygen, respectively. In our study, TiO2 thin films were prepared by electron beam induced deposition, evaporation induced self-assembling, radio-frequency sputtering and high temperature RF sputtering methods. The material properties were characterized by X-ray diffraction to reveal the crystallinity, scanning electron microscope to observe the surface morphology, energy dispersive spectrometry to analyze the chemical composition, and UV-Vis absorption spectrometry to check the light absorbance of the prepared TiO2 thin films. The photoelectrochemical property of the TiO2 thin films were investigated with a potentiostat. To prepare the photoelectrode for the water-splitting reaction, TiO2 thin film was deposited on side of Ti substrate while Pt thin film was coated on the opposite side to form the TiO2/Ti/Pt structure. By using an H-type reactor system to carry out water splitting reaction, hydrogen and oxygen were produced separately, eliminating additional separation process. The evolved gases were then detected by a GC analyzer. From the experimental results, the TiO2 thin film prepared by high-temperature RF sputtering method shows the highest photoactivity. To further enhance the hydrogen yield, triple junction solar cell was incorporated into the H-type reactor system to conduct water-splitting reaction in which hydrogen and oxygen was generated at the cathode and anode, respectively. In addition, Na2SO4 was used as the electrolyte solution in both compartments of the H-type reactor. This not only eliminates the chemical bias often applied for the water-splitting reaction, but also prevents the corrosion problem of the anode surface. Most importantly, the produced hydrogen-to-oxygen ratio reaches the stoichiometric ratio of water, which is 2:1.
Subjects
Titania thin films
Multijunction solar cell
Photocatalytic
Water splitting reaction
Hydrogen production
SDGs
Type
thesis
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