Charge trapping and photoadsorption of O2 on dehydroxylated TiO2 nanocrystals -: An electron paramagnetic resonance study

被引：120
作者：
Berger, T
Sterrer, M
Diwald, O
Knözinger, E
机构：
[1] Vienna Univ Technol, Inst Mat Chem, A-1210 Vienna, Austria
[2] Max Planck Soc, Fritz Haber Inst, Dept Phys Chem, D-14195 Berlin, Germany
来源：
CHEMPHYSCHEM | 2005年 / 6卷 / 10期
关键词：
charge transfer; EPR spectroscopy; oxygen; TiO2; nanocrystals; UV-induced charge separation;
D O I：
10.1002/cphc.200500161
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 photogenerated charges with molecular oxygen was investigated on TiO2 nonocrystals by means of paramagnetic resonance (EPR) spectroscopy. Compared to photoactivation experiments in Vacuum at p < 10(-6) mbar and T = 740 K, the presence of O-2 enhances the concentration of persistently trapped electron and hole centres-by a factor of ten-due to the formation of adsorbed O-2(-) species. The photoadsorption of oxygen was also tracked quantitatively by pressure measurements, and the number of trapped charges, hole centres and 0,was found to correspond to ten electron-hole pairs per TiO2 nanocrystal. Conversely, in experiments at p < 10(-6) mbar with one trapped electron-hole pair per particle, charge separation is not persistent and completely reversible with respect to temperature. Heating to 298 K causes the total annihilation of photogenerated and trapped charges.
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收藏
页码：2104 / 2112
页数：9
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