Pd(Cu)在MgO(100)表面吸附CO和O2的理论研究

采用固体镶嵌势能模型和DFT/B3LYP方法研究了在Pd/MgO和Cu/MgO表面吸附CO和O₂分子的电子性质. 计算结果表明, 在完美MgO(100)表面Pd原子对CO和O₂的吸附能分别为206.5和84.8 kJ/mol, 因此可知Pd原子更容易吸附CO分子; 而当Pd原子附着于有氧缺陷的MgO表面时, 它对两种分子的吸附都非常弱. 相反, 附着于MgO表面的Cu原子对O₂分子的吸附更为有利, 其吸附能在140～155 kJ/mol之间. 研究结果还表明, 对于双分子吸附体系, 即CO＋CO, CO＋O₂, O₂＋O₂体系, 双分子之间的结合力可减小完美MgO表面上Pd原子与被吸附分子的相互作用, 使吸附能减少了46～96 kJ/mol. 而对于在MgO表面上的Cu原子, 只有O₂＋O₂ 体系使吸附能减少了大约50～71 kJ/mol.

Theoretical Study on the Adsorption of CO and O2 on MgO-Supported Pd and Cu Atoms

The physical properties of adsorption and co-adsorption properties of CO and O₂ molecules on the MgO-supported Pd and Cu atoms have been studied at the DFT/B3LYP level of theory using the embedded cluster model. The calculations show that the supported Pd atom on the perfect surface is energetically more favorable for adsorbing a CO molecule than an O₂ molecule, with the respective binding energies of 206.5 vs. 84.8 kJ/mol. While such interactions on Pd atom located above an oxygen vacancy of the MgO(100) surface are very weak, due to significant amount of electron charge transferring from the vacancy to Pd atom. In contrast, the supported Cu atom on both types of surfaces prefers to adsorb O₂ molecule, instead of CO molecule, with the O₂ binding energies of 140～155 kJ/mol. It was found that the binding between the two-coadsorbates for CO＋CO, CO＋O₂, O₂＋O₂ coadsorbed on the supported Pd atom on the perfect surface reduced the admolecule-Pd interactions by the reductive energies of 46～96 kJ/mol. Such reductions only for O₂＋O₂ coadsorbed on the supported Cu atom on both surfaces are considerable with the reductive energies of 50～71 kJ/mol.