Department of Chemistry and Interdepartmental Centre of Excellence Nanostructured Interfaces and Surfaces-NIS, University of Torino, via P. Giuria 7, 10125 Torino, Italy.
Phys Chem Chem Phys. 2013 Aug 28;15(32):13391-9. doi: 10.1039/c3cp51524a.
Integrated studies of CO adsorption on TiO2 materials of different morphology and surface complexity identify, for the first time, frustrated translational CO modes by detecting their combination with the CO stretching mode (νCO). All the considered materials exhibit IR spectra with low-intensity bands in the 2235-2205 cm(-1) range, a region where components due to strong Lewis acid Ti(4+) sites may be present as well. These observations lead to a powerful method for associating high-wavenumber bands to TiO2 surface features and interpreting IR spectra of drastically complex/defective TiO2 materials. The proposed band assignment is based on vibrational analyses of CO-TiO2 theoretical models, indicating that the frustrated translational mode with frequency in the 30-50 cm(-1) range involved in the observed combination bands is perpendicular to the Ti(4+) rows. Our results reveal that this low-energy CO mode is much more sensitive than νCO in probing the TiO2 surface topography, and that its higher-energy components can be specifically associated with the presence of steps on the (101) faces. In a broader perspective, the frustrated translational CO mode surface sensitivity could become a key tool for detecting specific defective sites on TiO2 surfaces.
对不同形态和表面复杂度的 TiO2 材料上 CO 吸附的综合研究首次通过检测其与 CO 伸缩模式（νCO）的组合，识别出受挫的平移 CO 模式。所有考虑的材料都表现出在 2235-2205 cm(-1) 范围内具有低强度带的红外光谱，在该区域可能存在由于强路易斯酸 Ti(4+)位而产生的组分。这些观察结果为将高波数带与 TiO2 表面特征相关联以及解释极其复杂/有缺陷的 TiO2 材料的红外光谱提供了一种强大的方法。所提出的带分配基于 CO-TiO2 理论模型的振动分析，表明在观察到的组合带中频率在 30-50 cm(-1) 范围内的受挫平移模式垂直于 Ti(4+) 行。我们的结果表明，这种低能量 CO 模式比 νCO 更能灵敏地探测 TiO2 表面形貌，其更高能量的组分可以与（101）面上台阶的存在特异性相关联。从更广泛的角度来看，受挫的平移 CO 模式的表面灵敏度可能成为检测 TiO2 表面特定缺陷位点的关键工具。
