School of Chemical, Biological and Materials Engineering, University of Oklahoma , Norman, Oklahoma 73019, United States.
Langmuir. 2014 Dec 16;30(49):14832-40. doi: 10.1021/la5037426. Epub 2014 Dec 3.
The behavior of surface water, especially the adsorption and dissociation characteristics, is a key to understanding and promoting photocatalytic and biomedical applications of titanium dioxide materials. Using molecular dynamics simulations with the ReaxFF force field, we study the interactions between water and five different TiO2 surfaces that are of interest to both experiments and theoretical calculations. The results show that TiO2 surfaces demonstrate different reactivities for water dissociation [rutile (011) > TiO2-B (100) > anatase (001) > rutile (110)], and there is no water dissociation observed on the TiO2-B (001) surface. The simulations also reveal that the water dissociation and the TiO2 surface chemistry change, and the new surface Ti-OH and O-H functional groups affect the orientation of other near-surface water molecules. On the reactive surface, such as the rutile (110) surface, water dissociated and formed new Ti-OH and O-H bonds on the surface. Those functional groups enhanced the hydrogen bond networking with the near-surface water molecules and their configurations. On the nonreactive TiO2-B (001) surface where no molecular or dissociative water adsorption is observed, near-surface water can also form hydrogen bonds with surface oxygen atoms of TiO2, but their distance to the surface is longer than that on the rutile (011) surface.
地表水的行为，尤其是吸附和解离特性，是理解和促进二氧化钛材料的光催化和生物医学应用的关键。我们使用基于 ReaxFF 力场的分子动力学模拟，研究了对实验和理论计算都很重要的五种不同 TiO2 表面与水之间的相互作用。结果表明，TiO2 表面在水离解方面表现出不同的反应活性[金红石(011)＞TiO2-B(100)＞锐钛矿(001)＞金红石(110)]，而在 TiO2-B(001)表面观察不到水离解。模拟还揭示了水离解和 TiO2 表面化学性质的变化，以及新的表面 Ti-OH 和 O-H 官能团会影响近表面水分子的取向。在反应性表面上，如金红石(110)表面，水离解并在表面上形成新的 Ti-OH 和 O-H 键。这些官能团增强了与近表面水分子的氢键网络及其构型。在没有观察到分子或离解水吸附的非反应性 TiO2-B(001)表面上，近表面水也可以与 TiO2 的表面氧原子形成氢键，但它们与表面的距离比在金红石(011)表面上的距离更长。
