Identification of a surface alkylperoxy radical in the photocatalytic oxidation of acetone/O2 over TiO2

被引:48
作者
Attwood, AL
Edwards, JL
Rowlands, CC
Murphy, DM
机构
[1] Univ Wales Coll Cardiff, Dept Chem, Cardiff CF10 3TB, S Glam, Wales
[2] Huntsman Tioxide, Billingham TS23 1PS, Cleveland, England
关键词
D O I
10.1021/jp022448n
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The interaction of a coadsorbed mixture of acetone and oxygen with a clean oxidized polycrystalline sample of TiO2 (P25) was investigated using electron paramagnetic resonance (EPR) spectroscopy. UV illumination of the sample at low temperature (100 K) generated an unstable radical intermediate at the dehydrated (and hydrated) TiO2 surface. The radical decayed irreversibly at temperatures greater than 150 K but was regenerated by subsequent irradiation at low temperatures. Using a series of isotopically labeled gases (CH3COCH3, CD3-COCD3, O-16(2), and O-17(2)) to aid in the interpretation of the EPR spectrum, the radical was identified as an alkylperoxy species RCH2OO. with the spin Hamiltonian parameters of g(1) = 2.0345, g(2) = 2.0070, g(3) = 2.0010, (H)A(1) = 0.34 mT, (H)A(2) = 0.10 mT, (H)A(3) = 0.29 mT, (170)A(\\)(i) = 9.45 mT (for (ROO.)-O-17), and (170)A(\\)(ii) = 5.52 mT (for (ROO.)-O-17). By consideration of the different mechanistic pathways involved in the oxidation of acetone, it was concluded that the observed radical is generated initially by hole transfer to the adsorbed acetone and the identity of the unstable peroxy intermediate must be CH3COCH2OO..
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页码:1779 / 1782
页数:4
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