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 TiO ₂ 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.