Increasing the Efficiency of the Photocatalytic Oxidation of Organic Films on Aqueous Solutions by Reactively Coating the TiO2 Photocatalyst with a Chlorinated Silicone

In order to reduce the fraction of water and salt accessible surface OH sites on TiO 2, the photocatalytic crystallites were reacted, in an HCl-releasing reaction, with a chlorine-terminated chlorinated poly(dimethylsiloxane) telomer, Glassclad 6C. When the overcoated photocatalyst was applied in the oxidation of organic films on aqueous 0.5 M NaCl, the number of O 2 molecules consumed per photon drastically increased. In the oxidation of n -octanal films, 1.25 molecules of O 2 were consumed (five electrons were transferred to oxygen), and in the oxidation of n -octanoic acid, 0.15 molecules of O 2 were consumed (0.6 electrons was transferred) per photon. The overcoating reduced the O 2 -consumed/CO 2 -produced ratio in the initial reaction period when most of the reactant was intact. The enhancement of O 2 uptake per photon and the production of oxidized organic compounds, instead of CO 2, are attributed to chloride ion exclusion from the reaction zone and to fast hole oxidation, producing a radical, followed by prompt electron injection by the radical, resulting in two-electron oxidation.