Nitrogen surface species

Conversely, Gourec et al. suggested a mechanism involving a non-metallic active site.85 In the proposed mechanism, based on XPS, SIMS, and CV analysis, dioxygen reacts with protonated nitrogen surface species to form oxidized nitrogen surface species and water. After further reaction with protons and electrons, the oxidized nitrogen is reduced, and water is produced. 

In brief, the ceria-catalyzed oxidation of NO to NOg involves NO chemisorption on the catalyst, oxidation of the nitrogen surface species created on NO chemisorption, and NOg desorption. In order to analyze what occurs at the surface of ceria in contact with NO + O2 mixtures at temperatures around 350°C, a set of CCxZrj x02 catalysts... 

Actually NHx surface species are not the only active species in the Knoevenagel reaction. Indeed the catalysts with 2.8, 17.5 and 20 wt.% bulk nitrogen have the same NHx surface species content but their activities are... 

It is frequently asserted that two weaknesses of STM are first that all atomic asperities in images need not necessarily correspond to atom surface positions and second that it is inherently difficult to establish the identity of imaged atoms when two or more surface species are involved. The latter need not, however, be a problem. In a study (for example) of the oxidation of ammonia at Cu(110) the oxygen and nitrogen adatoms form separate individual structures which run in the < 100 > and < 110 > directions, respectively, whereas under ammonia-rich conditions only imide species are formed, running in the < 110 > direction, with in situ XPS confirming their presence and the absence of surface oxygen (Chapter 5). 

An ESCA angular depth profile study of similarly treated t-PB showed that sulfur and nitrogen are surface species. 

Characterization of Surface Species by SERS. Before presenting the results obtained with 1, the spectral features which have proven to be useful in identifying surface species will be reviewed. Both in solution and by SERS, pyridines show a ring mode in the Raman spectrum near 1600 cm-. When the ring nitrogen is protonated, this band disappears and is replaced by a band near 1640 cm-1. The... 

Tanaka, T Okuhara, T Misono, M. Intermediacy of organic nitro and nitrite surface species in selective reduction of nitrogen monoxide by propene in the presence of excess oxygen over silica-supported platinum. Appl. Catal, B Environmental, 1994, Volume 4, Issue 1, L1-L9. 

Iron has a rich surface coordination chemistry that forms the basis of its important catalytic properties. There are many catalytic applications in which metallic iron or its oxides play a vital part, and the best known are associated with the synthesis of ammonia from hydrogen and nitrogen at high pressure (Haber-Bosch Process), and in hydrocarbon synthesis from CO/C02/hydrogen mixtures (Fischer-Tropsch synthesis). The surface species present in the former includes hydrides and nitrides as well as NH, NH2, and coordinated NH3 itself. Many intermediates have been proposed for hydrogenation of carbon oxides during Fischer-Tropsch synthesis that include growing hydrocarbon chains. 

A number of other studies have now shown that dative bonding is a phenomenon common to many organic reactions on Ge(100)-2 x 1, as it is for Si(100)-2 x 1. In some cases, e.g., with the methylamines and pyridine, the dative-bonded state is the final surface species. This dative-bonded state can be quite stable. For example, the nitrogen dative bonds formed via exposure of methylamines to Ge(100)-2 x 1 have binding energies near 25 kcal/mol [49]. The STM study of pyridine on Ge(100)-2x1 revealed that 90% of the dative-bonded surface adducts remain after one... 

In general, in Part II we apply the same pattern of analysis to the numerous published vibrational spectra derived from the adsorption of alkynes, alkanes, and aromatic hydrocarbons. In addition, we summarize recently obtained spectroscopic results characterizing hydrocarbon species obtained by thermal, photochemical, or electron-bombardment dissociation of halogen- or nitrogen-substituted alkanes on single-crystal metal surfaces. The hydrocarbon surface species so obtained are normally as anticipated from the replacement of the heteroatoms by surface metal atoms. The... 

IV. Hydrocarbon Surface Species Derived from the Dissociative Adsorption of Halogen- or Nitrogen-Substituted Alkanes... 

Heterogeneous reactions on the surface of seasalt aerosols have been suggested as a potential source of atomic chlorine in the marine boundary layer [10,105]. The tropospheric relevance of the reaction of nitrogen oxide species N203 with Nad and NaBr was demonstrated in a smog chamber experiment on dry and deliquiescent NaCl aerosol and on salt solutions [74,78,106,107] ... 

The luminol detector is based on the sensitive chemiluminescent reaction between N02 and luminol in solution. The luminol in alkaline solution reacts with N02 to produce intensive CL centred on 425 nm. The detector cell itself is a 15 cm x 8 cm x 2 cm rectangular block, with inlets and outlets for the carrier gas and luminol flows. The reaction cell contains a fabric wick that is wetted with the luminol solution (1 x 10-4M luminol, 0.2MNa2SO3, 0.05M NaOH, 1.5 x 10 4 ethylenediaminetetraacetic acid and 0.1% surfactant). The wick is viewed by a PMT through an acrylic window, which is transparent to the chemiluminescent light at 425 nm. When a N02 peak enters the cell, a fraction of the N02 dissolves in the solution on the surface of the wick, which then reacts with luminol to ultimately yield a strong CL. The results described indicate that this detector may be successfully used for the sensitive and selective detection of any nitrogen-containing species that may thermally decompose to yield N02, with a potential use for the detection of explosives (2,4-DNT and TNT). 

Nitrogen dioxide, N02, is a fairly small molecule with an unpaired electron and may be expected to be a selective molecule for electron-deficient or Lewis acid sites. Nevertheless, only very little spectroscopic information on the nature of surface species formed on adsorption of N02 is available. Naccache and Ben Taarit (242) have shown by infrared spectroscopy and ESR that N02 forms Cr+N02+ and Ni+N02+ complexes on chromium and nickel zeolites. Thus, N02 behaves as an electron donor and reducing agent in these zeolites. Boehm (243) has studied the adsorption of N02 on anatase and on tj-A1203, which were pretreated at very low temperatures of only 100°-150°C. At 1380 cm-1, a band which is to be attributed to a free nitrate ion, was observed. Boehm (243) has explained the formation of the nitrate ion by the disproportionation by basic OH ions ... 

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