Characterization of NO_x Species Adsorbed on BaO:  Experiment and Theory

Abstract

Charged NO x species (x ) 1,2,3) formed upon adsorption of NO 2 on BaO are characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and theoretical vibrational analysis using the density functional theory (DFT). Experiments at 30 °C reveal nitrite formation. At T > 250 °C, shifts associated with formation of nitrates are observed, indicating an interconversion of oxygen atoms among adsorbates. The theoretical study includes single and pairwise NO 2 adsorption on (BaO) 9 clusters. As has been reported previously [Broqvist, P.; Panas, I.; Fridell, E.; Persson, H. J. Phys. Chem. B 2002, 106, 137], an additional energy gain is calculated for the second adsorbed NO 2 . A vibrational analysis of the investigated adsorption configurations supports the interpretation of nitrite to nitrate interconversion on the BaO surface. Moreover, the calculations demonstrate the sensitivity in the NO 2 vibrational band splitting with respect to adsorption configuration.

Interaction of NO2 with Model NSR Catalysts: Metal–Oxide Interaction Controls Initial NOx Storage Mechanism

“…Whereas several experimental studies point to sequential formation of nitrite and nitrate [9,[15][16][17][18] (cf. also [4]), theoretical calculations [19][20][21][22] and few recent experiUsing scanning tunneling microscopy (STM), molecular-beam (MB) methods and time-resolved infrared reflection absorption spectroscopy (TR-IRAS), we investigate the mechanism of initial NO x uptake on a model nitrogen storage and reduction (NSR) catalyst. The model system is prepared by co-deposition of Pd metal particles and Ba-containing oxide particles onto an ordered alumina film on NiAlA C H T U N G T R E N N U N G (110).…”

Strong Size Effects in Supported Ionic Nanoparticles: Tailoring the Stability of NO x Storage Catalysts

“…Bands (1) and (2) are related to On the basis of the exposure and size dependent behavior it is concluded that the bands are surface-related with at least two different species contributing. Based on the literature, the straightforward assignment would be to monodentate nitrates [27][28][29][30][31][32]. An unambiguous assignment appears difficult, however, due to the complexity of NO related surface chemistry, showing a wealth of different surface species with partially overlapping bands (see e.g.…”

Communication: Towards catalytic nitric oxide reduction via oligomerization on boron doped graphene

“…A second approach is to employ a NOx storage/reduction (NSR) catalyst 5 which combines long periods of lean running conditions during which the NOx is trapped in an oxide, mainly barium oxide, with short fat periods during which the trapped NOx is released and reduced to N 2 by the fuel. The NOx absorption by BaO requires oxidation of the thermal nitrogen oxide, [6][7][8][9][10] i.e., NO, which becomes converted to NO 2 on a platinum catalyst. [11][12][13] Conversely, following the release of NO 2 from BaO, the reduction to N 2 takes place on a rhodium catalyst.…”