小团簇Co_(n)(n=1~7)吸附O,CO,CO_(2)的密度泛函研究

Density Functional Study of O,CO and CO_(2)Adsorption on Small Clusters Co_(n)(n=1~7)

利用密度泛函理论(DFT),研究了吸附物(A:O、CO和CO_(2))在小团簇Co_(n)(n=1~7)上的吸附行为,即团簇Co_(n)A的几何结构、稳定特性和电子性质。结果表明:团簇Co_(n)O吸附位点的构型保持不变;团簇Co_(n)CO吸附位点除7B1转变为7T2构型之外,其余都与初始结构一致;团簇Co_(n)CO_(2)随吸附位点(顶位、桥位和空位)结构的不同显著变化。团簇Co_(n)A的吸附能由大到小依次为:Co_(n)O、Co_(n)CO、Co_(n)CO_(2),而能隙的变化规律不强,团簇Co_(n)A的吸附稳定性、Co和O(C)间距离、C—O键长、电荷转移都呈现规律性变化,说明吸附物被活化。团簇CO_(2)对CO的氧化机制研究中,路径b仅需越过0.436 eV的能垒,而路径a需要1.686 eV,表明路径b更有利,团簇CO_(2)OT有望成为良好的CO氧化催化剂。

Using density functional theory(DFT),the adsorption behaviors of O,CO and CO_(2)over small cluster Con(n=1~7)were studied,with the focus on the adsorption structure,stability and electronic properties.The results indicate that the optimized structures of the cluster ConO adsorption site remain unchanged,and the adsorption sites of the cluster ConCO are consistent with initial structures,except for the fact of 7B1 changed to 7T2.The cluster ConCO_(2)varies significantly with the structure of adsorption sites(top,bridge,and hole).The adsorption energy of cluster Co_(n)A is in descending order as ConO,ConCO,ConCO_(2),while the changes of the energy gap are of little regularity,the adsorption stability of cluster Co_(n)A,the distance between Co and O(C),the length of C—O bonds,and the charge transfer all show regular changes,indicating that the adsorbents are activated.The oxidation mechanism of cluster CO_(2)oxidizing CO shows that path b only needs to cross the barrier of 0.436 eV and path a requires 1.686 eV,indicating that path b is more favorable.The cluster CO_(2)OT is expected to be a good CO oxidation catalyst.