Investigations of Photo-Excited TiO2 Based on Time Resolved Microwave Conductivity and Oxygen Isotopic Exchange
Investigations of Photo-Excited TiO2 Based on Time Resolved Microwave Conductivity and Oxygen Isotopic Exchange
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基于时间分辨微波电导率和氧同位素交换的光激发 TiO2 研究
DOI：
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发表时间：
2010
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通讯作者：
Estelle Mietton
中科院分区：
文献类型：
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作者：
P. Pichat;R. Enríquez;Estelle Mietton
多相光催化的主要缺点是电荷复合，这在很大程度上限制了其应用。因此，研究这一过程具有十分重要的意义。时间分辨微波电导率(TRMC)是一种适合于这一目的的技术，因为它允许在没有电接触的情况下进行测量。本文介绍并讨论了用TRMC对二氧化钛粉末进行测试的结果。它们表明了二氧化钛颗粒直径在决定导电性方面的重要性。TRMC还显示了TiO2光生电子对沉积的铂颗粒的吸引，以及在均匀掺杂0.85%Cr3+离子的TiO2中发生了非常迅速的电荷复合。用二氧化硅作为粘结剂，对粘贴在玻璃纤维薄组织上的二氧化钛进行的TRMC测试表明，TRMC也适用于复合材料；二氧化硅的类型对导电性只有次要的影响。此外，用TRMC研究了醇对界面电荷转移的影响，以说明界面电荷转移的发生。另一方面，气态18O2的氧同位素交换(OIE)发生在光激发的Ti16O2上。它被认为是由表面的不规则性促成的，因此可以被探测到。在其光催化氧化的主要步骤需要掺入氧原子的化合物存在下的OIE测量表明，二氧化钛中不稳定的氧原子不起主导作用。对比OIE和光催化去除空气中甲醇的效果表明：(1)热处理对TiO2光催化剂表面结构的影响；(2)Se盐在更不稳定的表面O原子上的优先吸附和随后的紫外光诱导还原。
Charge recombination is the main drawback of heterogeneous photocatalysis; it considerably limits the applications. Consequently, it is of paramount importance to study this process. Time resolved microwave conductivity (TRMC) is an appropriate technique for that purpose since it allows measurements without electrical contacts. Here are presented and discussed results obtained by TRMC for TiO2 powders. They indicate the importance of the TiO2 particle diameter in determining the conductivity. The attraction of TiO2 photoproduced electrons to deposited Pt particles was also shown by TRMC, as well as the very rapid charge recombination in TiO2 homogeneously doped with 0.85 ion % of Cr3+ cations. TRMC measurements for TiO2 affixed on thin fiberglass tissues using SiO2 as a binder demonstrated that TRMC is also adapted to composite materials; the type of SiO2 had only a secondary influence on the conductivity. Additionally, the effects of alcohols were investigated by TRMC to illustrate the occurrence of interfacial charge transfer. On the other hand, oxygen isotope exchange (OIE) of gaseous 18O2 occurs over photo-excited Ti16O2. It is believed to be facilitated by surface irregularities which can thus be probed. OIE measurements in the presence of compounds whose photocatalytic oxidation primary step requires the incorporation of an O atom suggested that labile O atoms of TiO2 do not play the dominant role. Contrasted effects on OIE and photocatalytic removal of methanol in air showed (i) the influence of thermal treatment on TiO2 surface re-structuring (ii) the preferential adsorption and subsequent UV-induced reduction of Se salts at more labile surface O atoms.