Metal oxide-adsorbate interactions adsorption geometry

For ionic systems such as silicates and metal oxides, the interactions between physisorbed molecules and the surface atoms are dominated by electrostatic and repulsive terms. Therefore, empirical potentials are very usefol to gain an overview of possible adsorption geometries. This is particularly appropriate for zeolites, where geometric aspects related to the pore sizes and channel widths provide a first screening. In the case of molecules adsorbed or chemisorbed on metals and for achieving quantitative predictions, one has to resort to quantum mechanical methods. At present, this has been demonstrated only for atoms and rather small molecules such as CO and H2O interacting with surfaces. 

In this chapter, recent results are discussed In which the adsorption of nitric oxide and its Interaction with co-adsorbed carbon monoxide, hydrogen, and Its own dissociation products on the hexagonally close-packed (001) surface of Ru have been characterized using EELS (13,14, 15). The data are interpreted In terms of a site-dependent model for adsorption of molecular NO at 150 K. Competition between co-adsorbed species can be observed directly, and this supports and clarifies the models of adsorption site geometries proposed for the individual adsorbates. Dissociation of one of the molecular states of NO occurs preferentially at temperatures above 150 K, with a coverage-dependent activation barrier. The data are discussed in terms of their relevance to heterogeneous catalytic reduction of NO, and in terms of their relationship to the metal-nitrosyl chemistry of metallic complexes. 

Cu and Cu Oxide Surfaces Works performed on Cu surfaces were devoted to Cu-benzotriazole interactions. Indeed, benzotriazole (BTAH or C6N3H5) has been a weU-known corrosion inhibitor for Cu since 1947, as evidenced by a British patent. BTAH adsorption on CU2O was investigated by Blajiev and Hubin with LDA [69]. Several initial geometries were considered. The adsorption of the molecule induces a breakup of the bulk oxide periodicity. It was deduced that interfacial phases between the metal and the oxide and between the oxide and the electrolyte may be created in the conditions in which BTAH is used. Strong chemical interactions exist between the oxide and adsorbed molecules. 

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