Roles of water and dissolved oxygen in photocatalytic generation of free OH radicals in aqueous TiO2 suspensions: An isotope labeling studyстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 11 января 2016 г.
Аннотация:In this work, the photocatalytic generation of free OH radicals (radical dotOHfree) in aqueous TiO2 suspensions was studied using an 18O isotope labeling and a “remote” photocatalysis approach. A probe compound, 1,3,5-trichlorobenzene (TCB), was adsorbed in pores of silica gel (SG) microparticles and, by this, was shielded from the direct hole oxidation. Penetration of the TiO2 particles (25 nm in size) to the TCB, adsorbed in the SG pores, was blocked due to a small size of the SG pores (4 nm). Therefore, the “remote” degradation of the TCB was solely driven by radical dotOHfree, and this allowed us to selectively determine the quantum yield of the radical dotOHfree generation. The isotope labeling with 18O has demonstrated that the major pathway of the radical dotOHfree formation is the direct hole oxidation of H2O, whereas the reduction of dissolved O2 by photogenerated electrons contributes in less than 5% of the total amount of radical dotOHfree. Nevertheless, the latter pathway becomes more important if holes are scavenged. This work sheds light on the intrinsic roles of photogenerated holes and electrons in the mechanism of the radical dotOHfree formation in aqueous TiO2 photocatalysis.