DFT Investigation Of The Surface Morphology And Reactivity Of ? Group Bimetallic Surfaces

Bimetallic catalysts have attracted more and more attention of researchers all over the world because of its unique chemical and physical properties in recent years. Precious metal catalysts occupy a pivotal position in catalysis due to their excellent activity, selectivity and corrosion resistance. There are six kinds of precious metals in VIII group metal elements while nickel in VIII family is also a good catalyst, therefore, it is necessary to design and manufacture VIII bimetallic catalytic materials in order to further improve the catalytic activity of the precious metals and reduce the cost of the precious metal catalysts to a certain extent at the same time. In this paper, using the density functional theory combined with periodic slab model, the interaction between the small molecules such as H2S, HCHO, CO and the bimetallic surfaces by the VIII group metals like Ni, Pd, Pt, Rh compositions were studied compared with single metals. Specific research contents and results are as follows:(1)The most stable adsorption sites of the small molecule H2S on the surfaces of Ni (111) and Pd (111) are all Top site. The calculated adsorption energies of them are 0.58 eV and 0.51 eV, respectively. While H2S on Ni@ Pd (111), Pd@ Ni (111), Ni-Pd-Ni (111), Pd-Ni-Pd (111), these four kinds of bimetallic surfaces, the calculation results is very different with the single metallic surfaces, especially on the Ni@ Pd (111) plane. The most stable configuration of H2S on the Ni@Pd(111) bimetallic surface is the F(fcc) site and the adsorption energy can reach 3.20 eV. With the adsorption process, the H—S bond was disrupted, H2S molecule was broken down. The most stable adsorption sites of H and S atoms from the decomposition of H2S are all F(fcc) site.(2) The most stable adsorption sites of the small molecule HCHO on the surfaces of Ni (111), Ni@ Pt (111), and Ni@ Rh (111) were all F(fcc) sites. Although all the atoms on the surface of metals were all Ni atoms, the calculated adsorption energy of the surfaces were very different, they were all decreasing in the order of Ni@Pt (111)> Ni (111)> Ni@Rh (111). The existence of the underlying metal atoms changed the electron distribution of metal atoms on the surface, and effected the interaction between metal surfaces and small molecules. When the d electronic center of metal is closer to the Fermi level, the adsorption energy is larger.(3) Based on the adsorption behavior of CO,O on Ni (111), Ni@Pt (111), and Pt (111) surfaces, and the co-adsorption behavior of CO+O on Ni (111), Ni@Pt (111), and Pt (111) surfaces, here got a result that the most stable co-adsorption system of CO+O on the Ni (111) surface was CO H(hcp)+O F(fcc), the most stable co-adsorption system of CO+O on the Ni@Pt (111) surface was CO F(fcc)+O F(fcc), and the most stable co-adsorption system of CO+O on the Pt (111) surface was CO F(fcc)+O F(fcc). As the interaction between Ni (111) metal surfaces and oxygen atoms is larger, and Pt (111) surfaces have more effect on CO, Ni@Pt (111) bimetallic surfaces have a better activation on the oxidation of CO by combining the advantages of two kinds of metal.