O2在具有氧和镁缺陷MgO(001)表面的吸附

在密度泛函理论的框架下，采用嵌入点电荷簇模型研究了O2在具有氧缺陷和镁缺陷MgO(001)表面上的吸附.用电荷自洽的方法确定了点电荷的值.计算结果表明，O2倾向吸附在具有氧缺陷的MgO(001)表面上.通过和我们近期研究过的O2在低配位的边、角上吸附结果相比较，发现具有氧缺陷的MgO(001)表面更加有利于O2的吸附和解离. Mülliken电荷分析表明，电荷由底物向吸附的O2反键轨道上转移是导致O2键强削弱的主要原因.势能曲线表明，O2在具有氧缺陷的MgO(001)表面上发生解离所需要克服的能垒比在角阳离子端发生解离所需克服的能垒有大幅度降低.

O2 Adsorption on MgO(001) Surface with Oxygen and Magnesium Vacancies

The adsorption of O2 at oxygen vacancy site (F, F+ or F2+ site) and magnesium vacancy site (V, V- or V2- site) has been studied using cluster models embedding in a large array of point charges coupled to density functional method at B3LYP/6-31G(d) level. The value of point charges is determined by the self-consistent technique. The calculated results indicate that the MgO(001) surface with oxygen vacancies has more excellent catalyst structure contributing to the adsorptive-decomposition of O2 in comparison with the low-coordinated corner site in the previous study. The adsorption energies for O2 adsorbed on MgO(001) surface with oxygen vacancies are larger than those on MgO(001) surface with magnesium vacancies. Moreover, the MgO(001) surface with magnesium vacancies hardly exhibits catalytic reactivity toward O2 decomposition. The Mü lliken charge analysis illustrates that, for O2 adsorption on MgO(001) surface with oxygen vacancies, the electrons are transferred from the substrate to the adsorbed O2 and occupy the anti-bonding orbital, π of O2. Thus, the O- O bond strength is weakened. Potential energy curve shows that the energy barrier is considerably decreased for O2 adsorbed at oxygen vacancy site of MgO(001) surface when compared to that at corner site in our previous study.