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Enhancement of Photocatalytic/Photoelectrocatalytic Properties of TiO2/TiO2-CdS on Various Substrates for Pollutant Degradation and Hydrogen Production
AuthorWilson III, William W.
AdvisorSubramanian, Vaidyanathan Ravi
Civil and Environmental Engineering
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Abstract A surge in semiconductor research for a multitude of uses has taken place over the last few decades. Due to their unique band gap properties, semiconductors provide a material of multivariate use. Specifically, in the field of environmental engineering, the use of semiconductor materials as a means of enhancing pollutant degradation through photocatalytic processes has been examined. TiO2 has come to the forefront of much of this research due to its stable structure and non-toxic characteristics. However, due to its large band-gap, making it only photoactive in the near-UV portion of the solar spectrum, it shows relatively slow reaction kinetics, which has prevented the material from meeting its theoretical potential. The following research highlights a series of methods for enhancing the photocatalytic activity of TiO2 for use in photocatalytic pollutant degradation. The first portion of this thesis examines the effects of different substrate architectures on the photoactivity enhancement of immobilized TiO2 nanotube systems. It is shown that an increase of ~50% fractional conversion of pollutant can be achieved on TiO2 nanotubes on a cylindrical substrate compared to TiO2 on a planar foil substrate. Another known method of increased TiO2 activity comes from addition of small band gap semiconductors to the TiO2 surface. Following this, the second part of the research examines the effects of an interstitial layer of TiO2 nanoparticles on the nanotube surface leading to greater dispersion and loading of CdS nanocrystals. The addition of this TiO2 nanoparticle layer led to a ~30% increase in photocatalytic degradation compared to a TiO2 nanotube -CdS system without TiO2 nanoparticle addition. Finally, a set of tests showing pollutant degradation with simultaneous hydrogen production are covered as an example of future research to be pursued.