Photocatalysts for Air Pollution Control and Abatement

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Titanium dioxide (TiO2) has been largely studied in the past decades for its photocatalytic properties [1]. The material is a n-type of superconductor whose photocatalytic property is due to the absorption of photons (hv) with energy higher than the energy of the valence band. The electrons in the valence band use such energy to jump into the conduction band. This process, originally studied for the photolysis of water [2], has revealed itself of great use for the efficient removal of hazardous molecules and micro-organisms in water and in the air [3]. The high energy required by the electrons in the valence band to jump in the conduction band, which is 3.2eV for anatase TiO2, has limited the use of the material to the very narrow wavelength bandwidth of the ultraviolet (UV) radiation. In order to make use of the material under a much larger spectrum of light frequencies, especially under visible light, modifications of the TiO2 lattice by adding extra elements have been made and they still represent today a challenge for the research community. The change of the lattice can be done by doping TiO2 with different elements, this includes non-metal elements like carbon and nitrogen [4]. The importance of these studies stands on the fact that the resulting material, simply exposed to sun light or LED light, is able to sterilize the air from harmful bacteria and neutralize other well-known indoor volatile organic pollutants such as formaldehyde. This work presents some experimental observations on visible light photocatalytic carbon doped titanium dioxide, C-TiO2, obtained by a sol gel method. The study focuses on the crystal structure of the synthesized material. The aim is to evaluate the consistency of the method in reproducing the desired crystal structure and therefore the desired photo-catalytic properties of this material.