Photocatalytic Functional Coating of TiO₂ Thin Film Deposited by Cyclic Plasma Chemical Vapor Deposition at Atmospheric Pressure

Photocatalytic TiO₂ thin films were prepared with titanium tetraisopropoxide (TTIP) using cyclic plasma chemical vapor deposition (CPCVD) at atmospheric pressure. The CPCVD TiO₂ films contain carbon-free impurities up to 100 °C and polycrystalline anatase phases up to 200 °C, due to the radicals and ion-bombardments. The CPCVD TiO₂ films have high transparency in the visible wavelength region and absorb wavelengths below 400 nm (>3.2 eV). The photocatalytic effects of the CPCVD TiO₂ and commercial sprayed TiO₂ films were measured by decomposing methylene blue (MB) solution under UV irradiation. The smooth CPCVD TiO₂ films showed a relatively lower photocatalytic efficiency, but superior catalyst-recycling efficiency, due to their high adhesion strength on the substrates. This CPCVD technique may provide the means to produce photocatalytic thin films with low cost and high efficiency, which would be a reasonable candidate for practical photocatalytic applications, because of the reliability and stability of their photocatalytic efficiency in a practical environment.