Photocatalytic Activity of TiO2 and TiO2-xCxNy Thin Films From Polymer Assisted Deposition

Since the 1972 discovery of Fujishima and Honda detecting the occurrence of water splitting on TiO2 electrodes, titanium dioxide's use as a photocatalyst has provoked a broad range of research studies and applications. Applications like air and water-purifying, deodorizing, anti-bacterial use and self-cleaning are now being realized using. Pure TiO2's band gap is large (3.2 eV), causing its photocatalytic property to be active in the ultraviolet region which is <10% of the overall solar intensity. In this presentation, we discuss the synthesis and application of TiO2-based photocatalyst with enhanced visible light response. TiO2 and C-doped TiO2 films were grown on ITO glass by a chemical solution technique, polymer-assisted deposition (PAD) by heating the Ti-polymer precursor films at temperatures of 300 to 550 ºC. Structure analyses by SEM, XRD, as well as UV-Vis spectra are reported. At 500 ºC, the band gap was found to be ~3.05 eV and followed a linear relationship with increasing temperature as more of the polymer was burned off. TiO2 annealed at 350 ºC had remaining polymer in the film, resulting in a lower band gap energy of ~1.95 eV. At temperatures lower than 400 ºC, TiO2-xCx exists with a reduced band gap and should exhibit visible light photocatalytic properties. However, crystallinity of the C-doped TiO2 films is reduced to the point of films being amorphous, and results in the films showing no visible-light activity. This result is unique as it shows that one can reduced the band gap energy, but it does not guarantee enhanced photocatalytic efficiency.