H2O-involved two-electron pathway for photooxidation of aldehydes on TiO2: an isotope labeling study.
H2O-involved two-electron pathway for photooxidation of aldehydes on TiO2: an isotope labeling study.
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DOI：
10.1021/es5049539
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发表时间：
2015-02
影响因子：
11.4
通讯作者：
Tao Shi;Wei Chang;Hongna Zhang;Hongwei Ji;Wanhong Ma;Chuncheng Chen;Jincai Zhao
中科院分区：
文献类型：
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作者：
Tao Shi;Wei Chang;Hongna Zhang;Hongwei Ji;Wanhong Ma;Chuncheng Chen;Jincai Zhao
近年来，醛类污染问题日益受到人们的关注.在这项研究中，醛的光氧化为羧酸盐的二氧化钛表面上的氧同位素标记的方法进行了研究。发现溶剂H2O对所形成的羧酸盐的氧源贡献很大，如果传统的O2参与的自由基链反应是醛的光催化氧化的唯一机制，则不能解释这一点。我们还观察到，与在TiO 2光催化体系中不同，在均相溶液中由单电子氧化剂（·）OH和SO 4（·-）自由基引发的醛氧化将H2O的小O原子插入产物酸中。详细的实验，结合DFT计算，揭示了存在一个新的途径，为醛在TiO 2上的氧化，其中，类似于醛的脱氢酶的氧化，醛进行水合，然后通过一个双电子转移过程被氧化。本研究强调了TiO 2光催化氧化的多电子特性，并对环境中醛的氧化具有指导意义。
Aldehyde pollution has been receiving increasing environmental concern recently. In this study, the photooxidation of aldehydes to carboxylates on the TiO2 surface was studied by an oxygen-isotope-labeling method. The solvent H2O was found to contribute much to the oxygen source of the formed carboxylate, which cannot be explained if the conventional O2-involved free radical chain reaction is the only mechanism for the photocatalytic oxidation of aldehydes. We also observed that, unlike in the TiO2 photocatalytic system, the aldehyde oxidation in homogeneous solutions initiated by single electron oxidant (•)OH and SO4(•-) radicals inserted a small O atom of H2O into the product acids. The detailed experiments, combined with DFT calculation, revealed the existence of a new pathway for the oxidation of aldehyde on TiO2, in which, analogous to oxidation of aldehyde by dehydrogenase, the aldehyde undergoes a hydration first and subsequently is oxidized through a two-electron transfer process. The present study highlights the multielectron characteristic of TiO2 photocatalytic oxidation and can have implications for the oxidation of aldehyde in the environment.