Interaction of O₂ and N₂ molecules with Au deposited on regular and defective CaO (001) surfaces: Density functional calculations

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• 作者：S. Abdel Aal ; A.S. Shalabi ; W.S. Abdel Halim
• 关键词：Ab initio calculations ; Calcium oxide ; Gold ; Surface reactions ; Oxygen ; Nitrogen adsorption ; Charge transfer
• 刊名：Thin Solid Films
• 出版年：2013
• 出版时间：31 October, 2013
• 年：2013
• 卷：545
• 期：Complete
• 页码：341-352
• 全文大小：2282 K

文摘

The adsorption of O₂ and N₂ on gold atoms deposited at regular O^2 ?site and neutral oxygen vacancy (Fs site) that is the most reactive sites of the CaO (001) surface, has been studied by means of the density functional theory calculations and embedded cluster model. Two different orientations, perpendicular and parallel, for the O₂ and N₂ molecules approaching the surface have been considered. Fundamental aspects such as adsorption energy, natural bond orbital, charge transfer, band gaps, the spin densities, the densities of states, total charge-density contours, pairwise and non-pairwise additivity are elucidated to analyze the adsorption properties of O₂ and N₂. It is observed that the adsorption of O₂ is stronger at the Au atom that is supported on the Fs site than on the anionic site. Therefore, the presence of supported Au particle strongly stabilizes the adsorption of O₂. The molecular bonding mechanism to these complexes involves charge transfer to the oxygen molecule with a concomitant activation of the OO bond to a superoxo-like state. On the contrary, Au deposited at CaO (O^2 ?) and CaO (F_s) sites does not exhibit any tendency to bind N₂. The charge transfer between Au atom and N₂ molecule is not significant in these adsorption systems. The binding of O₂ precursor is mostly dominated by the metal pairwise additive contributions, and the role of the CaO is not restricted to supporting the metal.