A density functional study of NO₂ adsorption on perfect and defective MgO (1 0 0) and Li/MgO (1 0 0) surfaces

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• 作者：Kh.M. Eid^a ; ^{Khaled_eid@edu.asu.edu.eg} ; H.Y. Ammar^a ; ^b
• 关键词：Adsorption of NO2 ; Chemisorption ; MgO surfaces ; Density-functional theory ; Dissociation of NO2 ; Fs and Fs+-centers
• 刊名：Applied Surface Science
• 出版年：2012
• 期刊代码：6_01694332
• 类别：ms
• 出版时间：15 July, 2012
• 卷：258
• 期：19
• 页码：7689-7698
• 文件大小：1070 K

摘要

The density functional theory (DFT) in combination with embedded cluster model have been used to study the adsorption of nitrogen dioxide molecule (NO₂) on Li atom deposited on the surfaces of metal oxide MgO (1 0 0) on both anionic (O^{2鈭?/sup>) and defect (F_s and F_s+-centers) sites. The adsorption energy (E_ads) of NO₂ molecule (N-down as well as O-down) in different positions on O鈭?, F_s and F_s+-sites is considered. The geometrical optimizations have been done for the additive materials and MgO substrate surfaces. The formation energies have been evaluated for F_s and F_s+ of MgO substrate surfaces. The ionization potential (IP) and electron affinity (eA) for defect free and defect containing surfaces have been calculated. The adsorption properties of NO₂ are analyzed in terms of the adsorption energy, the electron donation (basicity), the elongation of NO bond length and the atomic charges on adsorbed materials. The densities of states (DOS) have been calculated and used for examining the adsorption properties. The NO₂ molecule is dissociated due to the interaction with the defective substrate surface (F_s-site) producing an oxygen atom strongly chemisorbed to the vacancy of the substrate and gaseous NO far away from the surface. The presence of the Li atom increases the surface chemistry of the anionic O2鈭?/sup>-site of MgO substrate surfaces (converted from physisorption to chemisorption). On the other hand, the presence of the Li atom decreases the surface chemistry of the F_s and F_s+-sites of MgO substrate surfaces. Generally, the NO₂ molecule is strongly adsorbed (chemisorption) on the MgO substrate surfaces containing F_s and F_s+-centers.}