Se和SeO2在O2/CaO (001)表面吸附反应的第一性原理研究

First-principles study of the adsorption and reaction of Se and SeO2 on O2/CaO(001) surface

    摘要
  • 摘要: 基于密度泛函理论的第一性原理和平板模型构造了最稳定的O2/CaO（001）表面，通过优化Se和SeO2在此表面可能的初始吸附结构得到最佳吸附构型，分析了Se原子在O2/CaO（001）表面向SeO2的转化。结果表明，Se原子在O2/CaO（001）表面的稳定吸附构型主要有两种，即O-Se-O和O-O-Se基团，其中，O-O-Se基团的Se终端具有一定化学活性；Se在O2/CaO（001）表面向SeO2转化所需反应能垒小于均相条件下生成SeO2所需反应能垒，表明CaO不仅作为吸附剂，也能促进Se向SeO2的转化；SeO2分子在O2/CaO（001）表面发生化学吸附时，吸附基底的部分价电子转移至SeO2分子轨道中。

     

    Abstract: O2/CaO(001) surface with the lowest energy was built by using the slab model and the first-principles method based on density functional theory. A series of possible adsorption configurations were optimized to get the adsorption geometries with the lowest energy for selenium (Se) and SeO2 on the O2/CaO(001) surface and the conversion of Se to SeO2 on the CaO(001) surface was then investigated. The results indicate that there are two adsorption configurations for Se atom on the O2/CaO(001) surface, viz., O-Se-O and O-O-Se groups; therein the Se terminal in O-O-Se group has a certain chemical activity. The reaction energy barrier for the heterogeneous conversion of Se and O2 to SeO2 is less than that for the homogeneous conversion, which means that CaO can not only act as an adsorbent, but also promote the conversion of Se to SeO2 as a catalyst; certain valence electrons in adsorption substrate are transferred to the orbits of SeO2 molecule when SeO2 molecule was adsorbed on the O2/CaO(001) surface.

     

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