Issue 5, 2018

Structural changes of water molecules during photoelectrochemical water oxidation on TiO2 thin film electrodes

Abstract

Behaviors of photogenerated charge carriers and structural changes of water molecules on TiO2 photoelectrodes were investigated by using time-resolved visible to mid-IR absorption spectroscopy. From the spectra measured in the visible to NIR region, it was shown that the lifetime of trapped electrons and holes becomes longer upon applying more positive potentials. This result was reasonably explained by the enhancement of the upward band bending at the water/TiO2 interface. On the other hand, from the spectra measured in the mid-IR region, structural changes of the water molecules were observed. When a TiO2 electrode was photoexcited at the potential where the water oxidation starts, a new absorption peak appeared at 3620 cm−1 with a slight decrease in the intensity of hydrogen-bonded water. This new peak was assigned to the isolated O–H band of water molecules. Usually, TiO2 surfaces exhibit super-hydrophilic properties with strong hydrogen-bonding; however, the obtained result was opposite. Therefore, the appearance of this isolated O–H band was ascribed to the cleavage of the hydrogen-bonding networks resulting from the production of reaction intermediates such as OH radicals or H2O2. The intensity of the isolated O–H decreases when applying more positive potentials, where the O2 evolution proceeds more efficiently. This could be ascribed to the rapid consumption of the reaction intermediates. At these potentials, the intensity of hydrogen-bonded water was also further decreased.

Graphical abstract: Structural changes of water molecules during photoelectrochemical water oxidation on TiO2 thin film electrodes

Supplementary files

Article information

Article type
Paper
Submitted
28 sep 2017
Accepted
15 des 2017
First published
15 des 2017

Phys. Chem. Chem. Phys., 2018,20, 3388-3394

Structural changes of water molecules during photoelectrochemical water oxidation on TiO2 thin film electrodes

C. S. K. Ranasinghe and A. Yamakata, Phys. Chem. Chem. Phys., 2018, 20, 3388 DOI: 10.1039/C7CP06646E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements