Light Intensity Dependent Behavior of Active Oxygen Species Formed at TiO₂ Film and Water Interface

抄録

We have investigated the light intensity dependent behavior of active oxygen species formed at TO₂ film photocatalyst and water interface. Chemiluminescence method was applied to elucidate the behavior of superoxide (O₂⁻), and for the detection of hydrogen peroxide (H₂O₂), fluorescence probe was used. When TO₂ was excited by relatively weak UV light (1 µW cm⁻²), deactivation process of O₂⁻ was almost unchanged even when the solution was stirred. It is likely that O₂^- is deactivated via electron transfer to the surface trapped hole. On the contrary, under relatively strong UV light illumination (15 mW cm⁻²), O₂⁻ decayed more rapidly when the solution was stirred. This implies that stirring the solution promotes the disproportionation reactions of O₂⁻ which results in the formation of H₂O₂. Consequently, it can be said that strong UV light illumination and stirring the solution induced the desorption of generated O₂⁻ from the surface. Amount of H₂O₂ measured using a fluorescence probe also confirm this photo-induced desorption behavior of O₂⁻.