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Three Types of Adsorptions of Nitric Oxide on the MgO Surface

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journal contribution
posted on 23.11.1999 by Yasunori Yanagisawa, Kei Kuramoto, Shin-ichi Yamabe
FT-IR spectroscopic studies of the adsorption of natural and 18O-enriched NO gases on thermally and cleaned MgO powders were carried out. The temperature dependence of the IR spectra was investigated to characterize the adsorbate species. Three types [1, 2, and 3] of NO adsorptions were obtained in the wavenumber region of 1500−1000 cm-1. Those types were examined using density functional theory [(U)B3-LYP/6-31G*] vibrational analyses of (MgO)n−NO cluster calculations. Types 1, 2, and 3 were assigned to monodentate, asymmetric, and symmetric bidentate geometries, respectively. A type 4, a “tridentate” model which involves a NO3-like species, was calculated and was found to give wavenumbers of less than 1000 cm-1. The splitting of IR bands of type 3 due to the 15N18O adsorbate was ascribed to the oxygen exchange, 15N18O → 15N16O, via the reaction 16O−15N−18O → 16O−15N−16O on MgO surfaces.