Laser photolysis of TiO2 layers in the presence of aqueous iodide

被引:22
作者
Behar, D
Rabani, J [1 ]
机构
[1] Hebrew Univ Jerusalem, Dept Phys Chem, IL-91904 Jerusalem, Israel
[2] Soreq Nucl Res Ctr, IL-81800 Yavne, Israel
[3] Hebrew Univ Jerusalem, Farkas Ctr, IL-91904 Jerusalem, Israel
关键词
D O I
10.1021/jp003176w
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
Laser photolysis of TiO2 porous layers has been studied using iodide as a hole-scavenger. The I-2(-) transient product, which is produced inside the layer, decays predominantly by the second-order reaction with TiO2 electrons and by disproportionation, The resulting I-3(-) ion also reacts with the TiO2 electron, although the rate of reaction is 2 orders of magnitude slower than I-2(-) Evaluation of the rate constants was achieved by fitting computed curves of absorbance vs time profiles to the experimental data. The rate constants k(e(TiO2)(-) + I-2(-)) (2.25 +/- 0.6) x 10(5), k(e(TiO2)(-) + I-3(-)) = (1.65 +/- 0.4) x 10(3), and k(I-2(-) + I-2(-)) = (1.1 +/- 0.15) x 10(5) M-1 s(-1) have been determined in the TiO2 layer. The rate constants suggest relatively low diffusion rates for I-2(-) radical ion and e(-)TiO(2). These have been attributed to electron trapping at nanocrystallite boundaries as well as activation and steric barriers. The rate of reaction of I-3(-) With the TiO2 electron suggests that this reaction must be important in photoelectrochemical cells involving iodide and iodine. The high photocurrent yields observed in some of these cells, is attributed to dense coverage of the TiO2 surface by the photosensitizer.
引用
收藏
页码:6324 / 6329
页数:6
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