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One‐Electron Redox Processes during Polyoxometalate‐Mediated Photocatalytic Reactions of TiO 2 Studied by Two‐Color Two‐Laser Flash Photolysis
Author(s) -
Tachikawa Takashi,
Tojo Sachiko,
Fujitsuka Mamoru,
Majima Tetsuro
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200501077
Subject(s) - flash photolysis , polyoxometalate , photocatalysis , electron transfer , redox , photochemistry , chemistry , electron , excited state , photodissociation , electron donor , inorganic chemistry , catalysis , kinetics , organic chemistry , reaction rate constant , atomic physics , physics , quantum mechanics
The one‐electron redox processes of several compounds during polyoxometalate (POM)‐mediated photocatalytic reactions of TiO 2 were investigated using the two‐color two‐laser flash‐photolysis technique. The efficiency of the one‐electron oxidation of aromatic sulfides by the trapped hole (h tr + ) or the surface‐bound OH radical (OH s . ) is found to be significantly enhanced due to electron transfer from the conduction band (CB) of TiO 2 to the POM. The efficiency of the electron transfer from the CB of TiO 2 to the POM decreases in the order H 2 W 12 O 40 6− < SiW 12 O 40 4− < PW 12 O 40 3− , that is, it depends on the reduction potential ( E red ) of the POMs. Electron injection from PW 12 O 40 4− in the excited state (PW 12 O 40 4−* ) to the CB of TiO 2 was clearly observed using the two‐color two‐laser flash‐photolysis technique. Storage of electrons in the TiO 2 /PW 12 O 40 3− /methyl viologen (MV 2+ ) ternary system was also achieved upon two‐color two‐laser irradiation.