氧气在纯净及掺杂铝表面的吸附——表面掺杂剂的作用。

Lousada Cláudio M, Korzhavyi Pavel A

Division of Materials Technology, Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden.

Phys Chem Chem Phys. 2015 Jan 21;17(3):1667-79. doi: 10.1039/c4cp04277h. Epub 2014 Dec 2.

Using density functional theory (DFT) with the PBE0 density functional we investigated the role of surface dopants in the molecular and dissociative adsorption of O2 onto Al clusters of types Al50, Al50Alad, Al50X and Al49X, where X represents a dopant atom of the following elements Si, Mg, Cu, Sc, Zr, and Ti. Each dopant atom was placed on the Al(111) surface as an adatom or as a substitutional atom, in the last case replacing a surface Al atom. We found that for the same dopant geometry, the closer is the ionization energy of the dopant element to that of elemental Al, the more exothermic is the dissociative adsorption of O2 and the stronger are the bonds between the resulting O atoms and the surface. Additionally we show that the Mulliken concept of electronegativity can be applied in the prediction of the dissociative adsorption energy of O2 on the doped surfaces. The Mulliken modified second-stage electronegativity of the dopant atom is proportional to the exothermicity of the dissociative adsorption of O2. For the same dopant element in an adatom position the dissociation of O2 is more exothermic when compared to the case where the dopant occupies a substitutional position. These observations are discussed in view of the overlap population densities of states (OPDOS) computed as the overlap between the electronic states of the adsorbate O atoms and the clusters. It is shown that a more covalent character in the bonding between the Al surface and the dopant atom causes a more exothermic dissociation of O2 and stronger bonding with the O atoms when compared to a more ionic character in the bonding between the dopant and the Al surface. The extent of the adsorption site reconstruction is dopant atom dependent and is an important parameter for determining the mode of adsorption, adsorption energy and electronic structure of the product of O2 adsorption. The PBE0 functional could predict the existence of the O2 molecular adsorption product for many of the cases investigated here.

我们使用密度泛函理论（DFT）和PBE0密度泛函，研究了表面掺杂剂在O₂分子吸附和解离吸附到Al₅₀、Al₅₀Alad、Al₅₀X和Al₄₉X型Al团簇上的过程中的作用，其中X代表Si、Mg、Cu、Sc、Zr和Ti等元素的掺杂原子。每个掺杂原子以吸附原子的形式或替代原子的形式置于Al(111)表面，在后一种情况下替代一个表面Al原子。我们发现，对于相同的掺杂几何结构，掺杂元素的电离能越接近元素Al的电离能，O₂的解离吸附就越放热，生成的O原子与表面之间的键就越强。此外，我们表明穆利肯电负性概念可用于预测O₂在掺杂表面的解离吸附能。掺杂原子的穆利肯修正二级电负性与O₂解离吸附的放热性成正比。对于处于吸附原子位置的相同掺杂元素，与掺杂原子占据替代位置的情况相比，O₂的解离更放热。我们根据作为吸附质O原子和团簇的电子态之间重叠计算得到的态重叠布居密度（OPDOS）对这些观察结果进行了讨论。结果表明，与掺杂剂和Al表面之间键合的离子性更强的情况相比，Al表面与掺杂原子之间键合的共价性更强时，O₂的解离更放热，与O原子的键合更强。吸附位点重构的程度取决于掺杂原子，并且是确定O₂吸附产物的吸附模式、吸附能和电子结构的重要参数。PBE0泛函能够预测此处研究的许多情况下O₂分子吸附产物的存在。