Adsorption Of H And CO On The Pd(111) And Aupd(111) Surfaces By Density Functional Calculations

With the growing consumption of underground energy, research and development of clean hydrogen energy is particularly urgent. We know that the production of hydrogen is not difficult, while the separation, purification and storage of hydrogen are difficult and challenging subjects. The metal catalysts occupy an important proportion of industrial catalysts. Palladium surface has a very good compatibility for hydrogen, therefore, that is a nice catalyst in using hydrogenation and dehydrogenation reaction. In recent years, alloy catalysts, adding another metal in the pure metal catalysts, are paid more and more attention for its unique surface stability and catalytic selectivity, such as the palladium and its alloy catalysts in this article. Hydrogen and carbon monoxide as significant industrial raw materials, we must attach importance to its research. In the catalytic reaction, H and CO adsorption on the catalyst surface determine the rate of the entire process. Therefore, it is necessary to investigate the reaction mechanism between H and CO and the metal surface.The stabilization of various AuPd(lll) surfaces have been investigated by a periodic density functional theory (DFT) approach, along with H and CO adsorption and coadsorption on Pd(lll) and AuPd(lll) surfaces. The first-principles calculations were conducted using the VASP program package. The results indicate that the ensembles of AuPd(lll) being composed of second-neighbor Au pairs are energetically favorable. On pure Pd(lll) surface, the most stable sites for both H and CO adsorption are the fcc site and the adsorption energies are2.85eV and2.03eV, respectively. The adsorption energies on AuPd(lll) surface for H and CO have a distinct reduction. The reduction values for H and CO are0.20-0.30eV and0.42-1.01eV, respectively. Therefore, bimetallic AuPd(lll) surface can improve the CO desorption. In different alloy surfaces, the adsorption of H is less stable accompanied by the increase of Au atom of the adsorption site and CO shows a good selectivity. For CO-preadsorbed, the reduction of the adsorption energy for H is0.39eV at hcp site on Pd(lll) and0.68eV at fee site on AuPd(lll) surface. This shows that CO is a poison for H adsorption.