Efficient Hydroxyl Radical Production and Their Reactivity with Ethanol in the Presence of Photoexcited Semiconductors

Abstract

Abstract ESR spin trapping technique has been applied to determine the quantum efficiency of the hydroxyl radical production from semiconductors such as anatase and rutile TiO2, WO3, and ZnO photoexcited with a 365 nm UV lamp in water and aqueous H2O2 solution. The quantum efficiency for anatase TiO2, rutile TiO2, and WO3 in H2O2 solution was 3—4 times larger than that in water. Its maximum values, 4.6% in water and 14.8% in 1 mmol dm−3 H2O2 solution were obtained from anatase TiO2. The reaction of the hydroxyl radical from photoexcited semiconductors with ethanol has been investigated in relation to the C-centered radical production in aqueous ethanol solution. The possible photocatalytic redox mechanisms are discussed concerning the reactions caused by photoinduced electron-hole pairs and produced radicals.