Nature of the Oxidizing Species Formed upon UV Photolysis of C-TiO2 Aqueous Suspensions

作者：Goldstein Sara^*; Behar David; Rabani Joseph

来源：Journal of Physical Chemistry C, 2009, 113(28): 12489-12494.

DOI：10.1021/jp9019969

UV photolysis of aerated aqueous suspensions of C-TiO2 (KRONOS vlp 7000) or TiO2 (KRONOS uvlp 7500, Degussa P25) containing CH3OH produces HCHO and H2O2, and the latter accumulates only in the case of C-TiO2. The UV photolysis of C-TiO2 in aerated Suspensions produces holes, which oxidize CH3OH to (CH2OH)-C-center dot leading to the formation of HCHO in the presence of oxygen. H2O2 produced via the oxidation of CH3OH to HCHO and through the reduction of O-2 by the conduction band or trapped electrons is adsorbed by all titania. Catalase, which catalyzes CH3OH oxidation by H2O2, substantially increases the rate of HCHO formation only in the case of C-TiO2. This observation indicates that the electrons produced upon UV excitation of C-TiO2 differ from those of unmodified TiO2 with respect to their reactivity toward the photolytically generated H2O2. The holes produced in P25 behave differently from those formed in C-TiO2 and uvlp 7000 with respect to their reaction with added H2O2. This difference is, at least in part, due to the relatively much lower saturation level of H2O2 at the P25 surface rather than different types of holes. Comparison between UV and visible excitation of C-TiO2 reveals qualitative differences with respect to the nature of the oxidizing and reducing species. The different nature of the holes obtained upon U-V and visible irradiation suggests that localization of the holes at the surface and subsequent oxidation of CH3OH is the predominant route as is the case with undoped titania.

• 出版日期2009-7-16