Pd与CeO2(111)面的相互作用的第一性原理研究

采用基于广义梯度近似的投影缀加平面波(projector augmented wave) 赝势和具有三维周期性边界条件的超晶胞模型，用第一性原理计算方法，计算并分析了Pd在CeO₂(111)面上不同覆盖度时的吸附能，价键结构和局域电子结构. 考虑了单层Pd和1/4单层Pd两种覆盖度吸附的情况. 结果表明：1)在单层吸附时，Pd的最佳吸附位置是O的顶位偏向Ce的桥位；在1/4单层吸附时，Pd最易在O的桥位偏向次层O的顶位吸附.2) 单层覆盖度吸附时，吸附原子Pd之间的作用较强；1/4单关键词：三元催化剂Pd2')" href="#">CeO₂吸附密度泛函理论

The Interaction between Pd and CeO2(111) surface: A first-principle study

The adsorption properties of Pd on CeO₂(111) surface are studied using the first principle projector-augmented-wave (PAW) method based density functional theory (DFT) within generalized gradient approximation (GGA) and with the inclusion of on-site Coulomb interaction (DFT+U). It is found that there exist different adsorption features for different coverages of Pd: (1) For one monolayer (ML) Pd adsorption on CeO₂(111) surface, Pd prefers to be adsorbed on the atop O site leaning toward the Ce-bridge site; while, for the 1/4 ML adsorption, Pd prefers to be adsorbed on the O-bridge site leaning toward the atop subsurface O site. (2) The interaction between the adsorbed Pd atoms is very strong when the coverage is one ML; on the other hand, there is almost no interaction between the Pd atoms for the 1/4 ML Pd adsorption, correspondingly, the interaction between Pd adatoms and CeO₂(111) substrate is stronger for lower coverage adsorption (1/4 ML) than that for higher coverage adsorption (1 ML). (3) The adsorption of Pd disturbes the CeO₂(111) surface structure in the vicinity of the adsorption site. (4) The Pd adsorption makes the Pd/CeO₂ more active as compared with the clean CeO₂(111) and bulk Pd metal, and there may exist some active sites at the Pd/CeO₂ interface. These studies may lead to a better understanding for the Pd/CeO₂ catalysts and give some hints to improve the efficiency of TWC.