The First Principle Study Of Surface Interaction Of Small Molecule With Pt And Pt Alloys

In this thesis, based on the first principle quantum mechanism calculations, the interaction between small molecule and the surface of Pt and Pt alloys has been systemically investigated by DFT method and several cluster models and periodical slab model. At the same time, the comparison study of different crystal surfaces has been performed. In order to understand the general rule and nature of the interaction between adsorbed species and metallic surfaces, the equilibrium structure, the most stable adsorption site and the adsorption strength have been systemically studied. The main conclusions of this work are summarized as follow.1. The adsorption of CO and H2O on the cluster models of Pt and Pt alloys have been investigated. And we find that the main factors that affect the stability of Pt alloys cluster model and the interaction between it and small molecule is different replacement site and the number of atoms. The alloy cluster model with a replacement atom at the middle of subsurface is the most stable model, though the adsorption of small molecule is the most unstable system, adsorption heat is 0.15eV. The adsorption of small molecule on the cluster with a replacement atom at the uppermost layer is the most stable adsorption system, adsorption heat is 0.51eV. The calculated results indicate that the more atoms in the cluster, the bigger the model is, and the sorption between small molecule and cluster is stronger.2. The adsorption of possible species of ethene hydrogenation on different Pt slab models has been investigated. The Pt(100) surface is the most suitable for this reaction. By the comparison calculation of the interaction between slab model with different alloy ratio and small molecule in ethene hydrogenation reaction, it is found that the alloys model with a proportion of 1:1 has a stronger interaction than that of pure Pt slab model.3. By comparing the calculated adsorption heats of small molecule, such as CO, on the slab and cluster model, the results that the interaction between small molecular and cluster model surface is weaker than slab model surface have been obtained in this paper(1.82eV vs. 1.92eV).