Photocatalytic mechanism of high-activity anatase TiO₂ with exposed (001) facets from molecular-atomic scale: HRTEM and Raman studies

Abstract

Anatase TiO₂ with a variant percentage of exposed (001) facets was prepared under hydrothermal processes by adjusting the volume of HF, and the photocatalytic mechanism was studied from atomic-molecular scale by HRTEM and Raman spectroscopy. It was revealed that: 1) From HRTEM observations, the surface of original TiO₂ with exposed (001) facets was clean without impurity, and the crystal lattice was clear and completed; however, when mixed with methylene blue (MB) solution, there were many 1 nm molecular absorbed at the surface of TiO₂; after the photocatalytic experiment, MB molecules disappeared and the TiO₂ lattice image became fuzzy. 2) The broken path of the MB chemical bond was obtained by Raman spectroscopy, i.e., after the irradiation of the light, the vibrational mode of C−N−C disappeared due to the chemical bond breakage, and the groups containing C−N bond and carbon rings were gradually decomposed. Accordingly, we propose that the driving force for breaking the chemical bond and the disappearance of groups is from the surface lattice distortion of TiO₂ during photocatalyzation.

Keywords

TiO₂ / exposed (001) facets / HRTEM / Raman spectroscopy / photocatalytic degradation mechanism

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Acknowledgements

This work was supported by the National Basic Research Program of China (973 Program, Grant No. 2009CB939705), the National Natural Science Foundation of China (Grant No. 11174227), and the Chinese Universities Scientific Fund.

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