Chemisorbed oxygen

O are being formed predominantly on the surface of oxides as a results of O2 adsorption. According to estimates of the authors of study [60] the fraction of oxygen chemisorbed on ZnO as 0 does not exceed 8%. It is assumed that formation of O2 and O at low temperatures are weakly connected processes. At temperatures higher than 200 C O2... 

It was assumed in paper [87] that the reducing gas R interacts with oxygen chemisorbed in charged form. Oxygen is created in the course of processes... 

Figure 4.6 Monte Carlo simulation of the structure of oxygen chemisorbed at a metal surface only at very low coverages is the oxygen present as isolated adatoms at 0 = 0.1 the majority are present as clusters.

Figure 11. C02 signal vs. time for the titration of oxygen chemisorbed on Ag...

The quantity of oxygen chemisorbed on the surface of an n-conducting oxide at constant temperature and oxygen pressure is obtained from (14a) and (15a)... 

Figure 23 shows a series of photoelectron difference spectra from oxygen chemisorbed on Pd, Pt, and Ir surfaces (136) that exhibit, as an essential... 

At first sight, scheme (371) does not agree with the results of our adsorption experiments these experiments showed that activated charcoal does not chemisorb CO at 100°C. It should, however, be taken into consideration that the surface of charcoal subjected to activation or even simply after storage in contact with air is covered with chemisorbed oxygen. The studies of the reactions of carbon with C02 and steam (see Section XX) have demonstrated that oxygen chemisorbed on carbon is indistinguishable from chemisorbed carbon monoxide. So it may be reckoned that activated charcoal is already covered with carbon monoxide before the contact with this gas. 

To understand these results, we must look at the band structure of the MgO surface (Fig. 5). In the band gap a number of lattice defects and surface states can be observed. The various transitions are shown by arrows. Vacuum pre-treatment at 300 °C will cause oxygen chemisorbed as O2 or 0 79) to be removed from the surface or to migrate into the lattice, thereby annihilating an oxygen vacancy. Physically and chemically adsorbed water will be removed, thus occupying another O2 vacancy in the surface ... 

Oxygen anion conductors solid electrolyte Oxygen, chemisorbed - chemisorption of oxygen Oxygen conducting solid electrolyte - solid electrolyte... 

Another interesting example of MCSCF calculation is the determination of the oxygen binding site on Si (100). Batra et al performed this work for a few model clusters for oxygen chemisorbed at one, two and four-fold coordinated sites on Si3H6, Si6H12, and Si7Hg clusters./172/... 

Figure 3. Partial density of states projected on the d-hond of Pts for bare [Xbuik- sJ-Pts (red) and oxygen-chemisorbed [Xbuik- s]-Pt3-02 (blue) clusters. The samples of surface atoms Xs considered are (a) Co2Pt, (b) C03, (c) Pt3, (d) Ni3 and (e) Fe3. The d-hond of bulk Pt (shaded green) is shown as reference. In all panels, the vertical dashed line at zero-energy marks the Fermi level.

The projected density of states on the J-band of Pts for bare [Xbuik-Xs]-Pt3 (red) and oxygen-chemisorbed [Xbuik-Xs]-Pt3-02 (blue) surfaces (Fig. 3) reveals in each case a J-DOS spectram of the adsorbed Pt3 island narrower and shifted to higher energies... 

Figure 6. Partial DOS projected onto the O atoms (red) and ci-band of Pt atoms (blue) for oxygen-chemisorbed [Xbuik-Xs]-Pt3-02 surfaces. The right panels show an expanded view of the O2 spectra (red) using as reference the spectrum of free O2 (green, labels are given in the top panel). A c> antibonding is indexed according to whether it originates from or p-orbitals. The bulk surfaces are 6, Co3Pt, 7, Co, 8, Pt, 9, Ni, and 10, Fe. The ci-band of bulk Pt—left panel, shaded area—is shown as a reference. The Fermi level is the energy zero in all cases.

Low-temperature luminescence spectra of naphthalene (Nph) adsorbed in the alkali and alkaline-earth forms of the X zeolites indicate molecules physically adsorbed and bound in donor-acceptor complexes. Using spectral methods the Nph oxidation reaction has been found to be promoted by water vapor. The oxygen chemisorbed in the cages is considered as an oxidizer of Nph. Nph forms photostable dimer associates on the surface of amorphous aerosil. 

The photonics of Nph molecules on the surfaces of the zeolite X as well as on aerosil has been studied. Nph in zeolite voids is present as physically adsorbed molecules and bound in donor-acceptor complexes (CTC). Water vapor admission to an adsorbed Nph causes oxidation under formation of luminescent products of a-naphthoquinon on the Na-forms and its mixture with b-naphthol in presence of the alkaline-earth cations. Assumption about participation of oxygen chemisorbed on acid centers in an oxidation reaction is substantiated. In presence of transition metal ions the Nph luminescence is totally quenched. The Nph molecules adsorbed on the dehydroxylated aerosil surface form bimolecular excimer-like associates with a stable ground state and resistance to UV irradiation. 

The agreement between the results obtained either by direct measurements at 200° or indirect calculations for oxygen chemisorbed at 250° is considered as a proof of the accuracy of the thermochemical cycles which were used for the indirect calculations (49). As the temperature is increased, the maximum surface coverage by adsorbed oxygen... 

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