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首页> 外文OA文献 >Composition, structure, and stability of the rutile TiO_2(110) surface: oxygen depletion, hydroxylation, hydrogen migration and water adsorption
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Composition, structure, and stability of the rutile TiO_2(110) surface: oxygen depletion, hydroxylation, hydrogen migration and water adsorption

机译：金红石TiO_2（110）表面的组成，结构和稳定性：   氧耗尽，羟基化，氢迁移和水吸附

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摘要

A comprehensive phase diagram of lowest-energy structures and compositions ofthe rutile TiO_2(110) surface in equilibrium with a surrounding gas phase atfinite temperatures and pressures has been determined using density functionaltheory in combination with a thermodynamic formalism. The exchange of oxygen,hydrogen, and water molecules with the gas phase is considered. Particularattention is given to the convergence of all calculations with respect tolateral system size and slab thickness. In addition, the reliability ofsemilocal density functionals to describing the energetics of the reducedsurfaces is critically evaluated. For ambient conditions the surface is foundto be fully covered by molecularly adsorbed water. At low coverages, in thelimit of single, isolated water molecules, molecular and dissociativeadsorption become energetically degenerate. Oxygen vacancies form in stronglyreducing, oxygen-poor environments. However, already at slightly more moderateconditions it is shown that removing full TiO_2 units from the surface isthermodynamically preferred. In agreement with recent experimental observationsit is furthermore confirmed that even under extremely hydrogen-richenvironments the surface cannot be fully hydroxylated, but only a maximumcoverage with hydrogen of about 0.6-0.7 monolayer can be reached. Finally,calculations of migration paths strongly suggest that hydrogen prefers todiffuse into the bulk over desorbing from the surface into the gas phase.
机译：利用密度泛函理论结合热力学形式论，确定了金红石型TiO_2（110）表面与周围气相在无限温度和压力下处于平衡状态的最低能级结构和组成的综合相图。考虑了氧，氢和水分子与气相的交换。特别注意所有关于侧向系统尺寸和平板厚度的计算的收敛性。另外，严格评估了半局部密度泛函描述还原表面能的可靠性。对于环境条件，发现表面完全被分子吸附的水覆盖。在低覆盖率下，在单个分离的水分子的限制下，分子和解离吸附会发生能量退化。氧空位在强烈还原的贫氧环境中形成。然而，已经显示出在稍微更适度的条件下，从表面上除去完整的TiO_2单元在热力学上是优选的。与最近的实验观察结果一致，进一步证实即使在极富氢的环境下，表面也不能完全被羟基化，但是仅能达到约0.6-0.7单层氢的最大覆盖率。最后，对迁移路径的计算强烈表明，与从表面解吸到气相相比，氢气更倾向于扩散到主体中。

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