Kinetic and Mechanistic Investigations of Multielectron Transfer Reactions Induced by Stored Electrons in TiO2 Nanoparticles: A Stopped Flow Study
- 2 March 2011
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Physical Chemistry A
- Vol. 115 (11), 2139-2147
- https://doi.org/10.1021/jp108958w
Abstract
The kinetics and the mechanism of various multielectron transfer reactions initiated by stored electrons in TiO(2) nanoparticles have been investigated employing the stopped flow technique. Moreover, the optical properties of the stored electrons in the TiO(2) nanoparticles have been studied in detail following the UV (A) photolysis of deaerated aqueous suspensions of TiO(2) nanoparticles in the presence of methanol. The reduction of common electron acceptors that are often present in photocatalytic systems such as O(2), H(2)O(2), and NO(3)(-) has been investigated. The experimental results clearly show that the stored electrons reduce O(2) and H(2)O(2) to water by multielectron transfer processes. Moreover, NO(3)(-) is reduced via the transfer of eight electrons evincing the formation of ammonia. On the other hand, the reduction of toxic metal ions, such as Cu(II), has been studied mixing their respective anoxic aqueous solutions with those containing the electrons stored in the TiO(2) particles. A two-electron transfer is found to occur, indicating the reduction of the copper metal ion into its non toxic metallic form. Other metal ions, such as Zn(II) and Mn(II), could not be reduced by TiO(2) electrons, which is readily explained on the bases of their respective redox potentials. The underlying reaction mechanisms are discussed in detail.Keywords
This publication has 27 references indexed in Scilit:
- Optical Properties and Reactions of Radiation Induced TiO2Electrons in Aqueous Colloid SolutionsThe Journal of Physical Chemistry B, 2000
- Formation and Absorption Spectrum of Copper Nanoparticles from the Radiolytic Reduction of Cu(CN)2-The Journal of Physical Chemistry B, 2000
- Heterogeneous photocatalysis Transition metal ions in photocatalytic systemsApplied Catalysis B: Environment and Energy, 1999
- Photocatalytic reduction of nitrite and nitrate ions to ammonia on M/TiO2 catalystsJournal of Photochemistry and Photobiology A: Chemistry, 1997
- Charge Carrier Dynamics at TiO2 Particles: Reactivity of Free and Trapped HolesThe Journal of Physical Chemistry B, 1997
- On the usage of turnover numbers and quantum yields in heterogeneous photocatalysisJournal of Photochemistry and Photobiology A: Chemistry, 1993
- Nitrite ion reduction to ammonia in illuminated aqueous suspensions of powdered semiconductors in alkaline sulphide solutionsJournal of the Chemical Society, Chemical Communications, 1986
- Dynamics of interfacial charge-transfer reactions in semiconductor dispersions. Reduction of cobaltoceniumdicarboxylate in colloidal titaniaInorganic Chemistry, 1985
- Flash photolysis observation of the absorption spectra of trapped positive holes and electrons in colloidal titanium dioxideThe Journal of Physical Chemistry, 1984
- Interfacial electron-transfer reactions in colloidal semiconductor dispersions. Kinetic analysisThe Journal of Physical Chemistry, 1982