h-Fe₇C₃ is considered as the main active phase of medium-temperature Fe-based Fischer–Tropsch catalysts. Basic theoretical guidance for the design and preparation of Fe-based Fischer–Tropsch catalysts can be obtained by studying the adsorption and activation behavior of CO on h-Fe₇C₃. In this paper, the first-principles method based on density functional theory is used to study the crystal structure properties of h-Fe₇C₃ and the adsorption and activation CO on its low Miller index surfaces (110, 111, 101, 111) and (001). It was found that the low Miller index crystal plane of h-Fe₇C₃ crystal has multiple equivalent crystal planes and that the maximum adsorption energy of CO at the 3F2 point of the (111) plane is −2.50 eV, indicating that h-Fe₇C₃ has a better CO adsorption performance. In addition, the defects generated at the truncated position of the h-Fe₇C₃ crystal plane have a great impact on the adsorption energy of CO on its surface, that is, the adsorption energy of CO on Fe atoms with C vacancies is higher. The activity of CO after adsorption is greatly affected by the adsorption configuration and less affected by the adsorption energy. The higher the coordination number of Fe atoms after adsorption, the higher the CO activity. At the same time, it was found that the bonding of O and Fe atoms is conducive to the activation of CO.

中文翻译：

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h-Fe7C3催化剂上CO吸附的第一性原理研究

h-Fe ₇ C ₃被认为是中温铁基费-托催化剂的主要活性相。通过研究CO在h-Fe ₇ C ₃上的吸附和活化行为，可以获得有关铁基费-托催化剂设计和制备的基本理论指导。本文采用基于密度泛函理论的第一性原理方法研究了h-Fe ₇ C ₃的晶体结构特性及其在低米勒指数表面（110、111、101、111）的吸附和活化CO。和（001）。发现h-Fe ₇ C ₃的低密勒指数晶面晶体具有多个等效晶面，并且在（111）面的3F2点处CO的最大吸附能为-2.50 eV，表明h-Fe ₇ C ₃具有更好的CO吸附性能。另外，在h-Fe ₇ C ₃的截断位置产生的缺陷晶面对CO在其表面的吸附能有很大的影响，即CO在具有C空位的Fe原子上的吸附能较高。吸附后CO的活性受吸附构型的影响很大，而受吸附能的影响较小。吸附后Fe原子的配位数越高，CO活性越高。同时，发现O和Fe原子的键合有助于CO的活化。