Spectral Identification of Methanol on TiO2(110) Surfaces with Sum Frequency Generation in the C鈥揌 Stretching Region
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- 作者：An-an Liu ; Shuo Liu ; Ruidan Zhang ; Zefeng Ren
- 刊名：Journal of Physical Chemistry C
- 出版年：2015
- 出版时间：October 15, 2015
- 年：2015
- 卷：119
- 期：41
- 页码：23486-23494
- 全文大小：537K
- ISSN：1932-7455
文摘
In order to understand the adsorption behavior and photocatalytic reactions of organic molecules on titanium dioxide, TiO2, at the molecular level, we have studied the vibrational spectra of methanol on TiO2(110) by using surface-specific broadband infrared (IR) sum frequency generation (SFG) in combination with ultrahigh vacuum technique. As compared to vapor/liquid methanol interface, methanol on TiO2(110) exhibits a much more complicated spectrum due to its molecular and dissociative adsorption (methoxy) on TiO2(110). Furthermore, different sites are available for the methanol adsorption, including five-coordinated titanium (Ti5c) and bridge-bonded oxygen (Obr). The methyl group of these species has symmetric stretching and Fermi resonance modes similar to those at the air/liquid methanol interface, and also presents intense antisymmetric stretching modes. These resonances of both molecular and dissociative methanol have been well resolved and assigned by means of polarization-dependent and methanol coverage-dependent SFG measurements, as well as ultraviolet (UV) irradiation treatments. This work lays the foundation for further in situ studies of the surface chemistry of methanol on TiO2(110). The results also demonstrate the ability of SFG vibrational spectroscopy for investigating complicated structures of adsorbates on single crystal oxides.