Change in the chemical and electronic properties of TiO2/SnO2:F stacked-layers induced by the photocatalytic reaction

The TiO2/SnO2:F stacked-layers are synthesized by reactive sputter deposition of TiO2 films on glass substrates with a rutile SnO2:F coating. Precise control of sputter parameters allows the anatase phase formation of the TiO2 overlayer in the near-surface region even at a small thickness of 40 nm, leading to a higher photocatalytic activity such as a photodegradation of gaseous acetaldehyde. However, a repeat of photocatalytic measurements results in a deterioration of the photocatalytic activity of the sample. Through X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy analyses, we find a drastic change in the chemical and electronic properties of a 40-nm-thick TiO2 overlayer by a repeat of photocatalytic reactions.