Quantum yield measurements for the photocatalytic oxidation of Acid Orange 7 (AO7) and reduction of 2,6-dichlorindophenol (DCIP) on transparent TiO2 films of various thickness
Quantum yield measurements for the photocatalytic oxidation of Acid Orange 7 (AO7) and reduction of 2,6-dichlorindophenol (DCIP) on transparent TiO2 films of various thickness
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DOI：
10.1016/j.cattod.2014.04.019
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发表时间：
2015-02-01
期刊：
影响因子：
5.3
通讯作者：
Mills, A.
中科院分区：
文献类型：
--
作者：
Krysa, J.;Baudys, M.;Mills, A.
这项工作包括使用两个测试系统的透明溶胶-凝胶TiO 2涂层的各种厚度的光活性评估。酸性橙子7（A07）的氧化漂白和2，6-二氯靛酚（DCIP）的还原漂白反应的初始速率均随二氧化钛膜厚度和吸收光通量的增加而线性增加。后一项工作显示A07和DCIP测试系统的量子产率（QY）分别为0.19%和92%。A07氧化的低QY是由于氧的缓慢不可逆还原以及A07氧化的组合，因此有利于电子-空穴复合的高效率，这对于水性有机污染物是典型的。相比之下，DCIP的光催化还原的非常高的QY是由于存在大量过量的甘油，其有效地捕获光生空穴并因此允许染料的较慢还原发生的时间。此外，甘油的氧化导致产生高度还原的R-羟烷基，其也能够还原DCIP。由于这种“电流加倍”效应，观察到的QY（92%）远高于50%的表观理论值。(C)2014由Elsevier B. V.出版
This work comprises the photoactivity assessment of transparent sol-gel TiO2 coatings of various thickness using two test systems. The initial rates of both photocatalytic reactions, namely the oxidative bleaching of Acid Orange 7 (A07) and the reductive bleaching of 2,6-dichlorindophenol (DCIP) increase linearly with increasing titania film thickness as well as with increasing absorbed light flux. The latter work revealed quantum yields (QY) of 0.19% and 92% for the A07 and DCIP test system, respectively. The low QY for the A07 oxidation is due to the combination of a slow irreversible reduction of oxygen and also for the oxidation of A07, thus favouring the high efficiency for electron-hole recombination that is typical for aqueous organic pollutants. In contrast, the very high QY for the photocatalysed reduction of DCIP is due to the presence of a vast excess of glycerol which traps the photogenerated holes efficiently and so allow time for the slower reduction of dye to take place. Furthermore, the oxidation of glycerol results in the generation of highly reducing R-hydroxyalkyl radicals that are able to also reduce DCIP. As a consequence of this 'current doubling' effect, the observed QY (92%) is much higher than the apparent theoretical value of 50%. (C) 2014 Published by Elsevier B.V.