The Photocatalytic Reaction of the Thin Film TiO₂-Sr₄Al₁₄O₂₅Phosphors for Benzene Gas

Abstract

Phosphorescent materials coated with titanium dioxide were fabricated and photocatalytic reactions between these materials and VOCs gases were examined. A thin film (approx. 100 nm) of nanosized TiO 2 was deposited on the Sr 4 Al 14 O 25 : Eu 2+ , Dy 3+ ,Ag + phosphor using low-pressure chemical vapor deposition (LPCVD). The characteristics of the photocatalytic reaction were examined in terms of the decomposition of benzene gas using a gas chromatography (GC) system under ultraviolet (λ = 365 nm) and visible light (λ > 420 nm) irradiation. TiO 2 -coated Sr 4 Al 14 O 25 : Eu 2+ , Dy 3+ ,Ag + phosphor showed different photocatalytic behavior compared with pure TiO 2 . TiO 2 -coated phosphorescent materials showed a much faster photocatalytic decomposition of benzene gas under visible irradiation compared to the pure TiO 2 for which the result was practically negligible. This suggests that the extension of the absorption wavelength to visible light occurred through energy band bending by a heterojunction at the interface of the Sr 4 Al 14 O 25 -TiO 2 composite. Also, the Sr 4 Al 14 O 25 -TiO 2 composite showed the photocatalytic decomposition of benzene in darkness due to the photon light emitted from the Sr 4 Al 14 O 25 phosphors.