Fundamental and Computational Sciences Directorate and Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Phys Chem Chem Phys. 2013 May 7;15(17):6190-5. doi: 10.1039/c3cp44040k.
The interactions of CO2 with oxygen adatoms (Oa's) on rutile TiO2(110) surfaces have been studied using scanning tunneling microscopy. At 50 K CO2 is found to adsorb preferentially on five-coordinated Ti sites (Ti5c's) next to Oa's rather than on oxygen vacancies (VO's) (the most stable adsorption sites on reduced TiO2(110)). Temperature dependent studies show that after annealing to 100-160 K, VO's become preferentially populated indicating the presence of a kinetic barrier for CO2 adsorption onto the VO's. The difference between the CO2 binding energy on VO's and Ti5c sites next to the Oa's is found to be only 0.009-0.025 eV. The barrier for CO2 diffusion away from Oa's is estimated to be ~0.17 eV. Crescent-like features of the images of CO2 adsorbed on Ti5c's next to Oa's are interpreted as a time average of terminally bound CO2 molecules switching between the configurations that are tilted towards Oa and/or towards one of the two neighbouring bridging oxygen (Ob) rows. In the presence of VO defects, the Ti5c bound CO2 is found to tilt preferentially away from the VO containing Ob row. If another CO2 is present on the neighbouring Ti5c row, both CO2 molecules tilt towards the common Ob row that separates them.
使用扫描隧道显微镜研究了二氧化碳与金红石 TiO2(110)表面氧吸附原子 (Oa) 的相互作用。在 50 K 时，CO2 优先吸附在紧邻 Oa 的五配位 Ti 位 (Ti5c) 上，而不是在氧空位 (VO) 上（还原的 TiO2(110)上最稳定的吸附位）。温度依赖性研究表明，在退火至 100-160 K 后，VO 优先被占据，表明 CO2 吸附到 VO 上存在动力学障碍。在 VO 和紧邻 Oa 的 Ti5c 位上 CO2 结合能的差异仅为 0.009-0.025 eV。CO2 从 Oa 处扩散的障碍估计约为 0.17 eV。吸附在紧邻 Oa 的 Ti5c 上的 CO2 的图像中的新月形特征被解释为末端结合的 CO2 分子在两种配置之间切换的时间平均值，这两种配置分别朝向 Oa 和/或两个相邻桥氧 (Ob) 行之一。在存在 VO 缺陷的情况下，发现 Ti5c 结合的 CO2 优先从含有 VO 的 Ob 行倾斜。如果在相邻的 Ti5c 行上存在另一个 CO2，则两个 CO2 分子都向将它们分开的公共 Ob 行倾斜。
