Modeling NOx Storage Materials: On the Formation of Surface Nitrites and Nitrates and Their Identification by Vibrational Spectroscopy

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• 作者：Aine Desikusumastuti ; Markus Happel ; Karifala Dumbuya ; Thorsten Staudt ; Mathias Laurin ; J. Michael Gottfried ; Hans-Peter Steinr&uuml ; ck ; Jö ; rg Libuda
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：April 24, 2008
• 年：2008
• 卷：112
• 期：16
• 页码：6477 - 6486
• 全文大小：703K
• 年卷期：v.112,no.16(April 24, 2008)
• ISSN：1932-7455

文摘

We have studied the reaction of NO₂ with BaO nanoparticles supported on an ordered Al₂O₃ thin film onNiAl(110). Combining chemical analysis by X-ray photoelectron spectroscopy (XPS) and vibrationalspectroscopy by infrared reflection absorption spectroscopy (IRAS), performed in combination with molecularbeam (MB) techniques, the sequence of appearance of various nitrogen-oxo surface intermediates and theirspectral properties are identified. The initial intermediates at 300 K are surface nitrites (NO₂^-), which arepreferentially oriented parallel to the surface. Whereas formation of nitrites is rapid even at 300 K, conversionof nitrites into surface nitrates (NO₃^-) occurs at a very low rate. After surface nitrate formation, no furtherreaction is observed. At higher temperature (500 K), conversion into surface nitrates is more facile and isfollowed by formation of ionic nitrates. All three nitrogen-oxo species can be clearly identified via theircharacteristic vibrational spectra. No spectroscopic evidence for the formation of other NO_x-derived surfacespecies is found under the reaction conditions applied in this study. The results suggest that (i) conversion ofthe surface nitrite into the surface nitrate and (ii) formation of the ionic nitrate are the rate-controlling stepsin the storage process.