First Principles Study Of Catalytic Reaction Mechanism On Noble Metal Surface And Nanoparticle

Fuel cell, as one of the best energy conversion devices to use hydrogen energy, gains popularity in response to the global energy crisis. To improve the performance of fuel cell, an efficient oxygen reduction cathode catalyst is required to accelerate the reaction rate; to realize non-pollution in fuel cell, excellent hydrogen storage technology is need to provide clean fuel for the anode. Very significant achievements have been made in the exploration of the cathode catalyst and new hydrogen storage materials. However, the corresponding reaction mechanisms are still unclear. Our research aims at providing theoretical support to the development of fuel cell, which include two parts as follows.1. The mechanism of oxygen reduction reaction on Au-based Pd/Au surface alloy. The process of Pd diffusion on the Au(111) and Au(100) surfaces and incorporation into the subsurfaces is first investigated in order to gain an insight into how the Pd/Au surface alloy is formed. It is indicated that Pd can readily diffuse from the surface to the second layer of Au(100) and Au(111) substrates in the presence of vacancies. However, further diffusion into deeper sub-layers is rather difficult. Subsequently, the catalyzed O2 dissociation is used as a probe to investigate the influence of the Pd/Au surface and sub-surface morphology on the catalytic activity. It is found the catalytic activity of Pd/Au(100) is superior to Pd/Au(111). Furthermore, the Pd atoms that incorporate into the second layer of Au substrates have different influences on the catalytic activity of Pd/Au(100) and Pd/Au(111) surfaces. The second-layer Pd atoms in Pd/Au(111)-â…¡hinder the O2 dissociative adsorption. In contrast, the second-layer Pd atoms in Pd/Au(100)-â…¡can promote the O2 dissociative adsorption and alleviate the reconstruction of the surface after adsorbing oxygen atoms.2. Hydrogen spillover mechanism on Pd doped IRMOF-1. The tetrahedral Pd4 deposition configurations on IRMOF-1 and its influence on the electronic structure of IRMOF-1 are first investigated. It is indicated that Pd4 has stronger interaction with the linker than the corner, and the adhesion energies are dependent on the binding configurations. Based on the different Pd4@IRJVMOF-1 interfacial structures, we next study the corresponding structures for saturated hydrogen adsorption on Pd4, which can be regarded as the initial states of H spillover. It is found that when Pd4@linker is saturated by H2, Pd4 is still receptor-supported. In contrast, Pd4 deposition on the corner will be detached upon hydrogen saturation. Finally, the thermodynamic feasibility of hydrogen spillover in IRMOF-1 promoted by Pd clusters is proved.