Oxygen adsorbed cobalt

Associated with these surfaces, three distinct forms of oxygen can exist lattice oxygen, 0, oxygen adsorbed on [Co], Oco and oxygen adsorbed on [0l], 0q. Halpern and Germain (4) have also reported the presence of three different kinds of oxygen on a cobalt oxide surface. 

A detailed discussion of the symmetry properties of 0/Co(0001) is difficult since oxygen adsorbs in a disordered state on this surface. In the case of an ordered structure (O/Fe(001)) Huang and Hermanson [66] calculated an induced magnetic moment of oxygen to be about 0.24 Moreover, the photoelectron intensity differences (i.e. the MCDAD asymmetry) in the Co 3d band near the Fermi level decrease after oxygen exposure due to the chemical interaction of oxygen with the topmost cobalt layer. The reduced asymmetry displays a reduced magnetic moment of cobalt. 

Zeng, Z.Y., S.L. Gupta, H. Huang, and E.B Yeager (1991). Oxygen reduction on poly (4-vinylpyridine)-modified ordinary pyrolytic graphite electrodes with adsorbed cobalt tetra-sulphonated phthalocyanine in acid solution. J. Appl. Electrochem. 21, 973-981. 

The mechanism has been proposed to involve Jt-backdonation from Ru(II) or Os (11) to the oxygen adsorbed porphyrin adduct Co(II)-02, where the cobalt porphyrin is the site for oxygen reduction while Ru and Os serve as cocatalysts which affect... 

A freeze-dried powder of the cobalt-porphyrin (6) polymer possessed a fine porous structure, and it adsorbed and desorbed oxygen rapidly. The (6) powder containing 30% cobalt-porphyrin was charged in a chamber, and the air supply and evacuation with a simple pump was repeated at 30-sec intervals This pressure swing method with the cobalt-porphyrin polymer as an oxygen adsorbent provided oxygen-enriched air (oxygen concentration in the product flow 45%). 

Cobalt(Il) dicobalt(Ill) tetroxide [1308-06-17, Co O, is a black cubic crystalline material containing about 72% cobalt. It is prepared by oxidation of cobalt metal at temperatures below 900°C or by pyrolysis in air of cobalt salts, usually the nitrate or chloride. The mixed valence oxide is insoluble in water and organic solvents and only partially soluble in mineral acids. Complete solubiUty can be effected by dissolution in acids under reducing conditions. It is used in enamels, semiconductors, and grinding wheels. Both oxides adsorb molecular oxygen at room temperatures. 

Lalande G, Cote R, Tamizhmani G, Guay D, Dodelet JP. 1995. Physical, chemical and electrochemical characterization of heat-treated tetracarboxylic cobalt phthalocyanine adsorbed on carbon black as electrocatalyst for oxygen reduction in polymer electrolyte fuel cells. Electrochim Acta 40 2635-2646. 

Two forms of carbon (carbidic and graphitic) have been observed by x-ray photoelectron spectroscopy (XPS) on polycrystalline cobalt foil during the disproportionation of CO by Nakamura et al.57 The dissociation of adsorbed CO occurred at temperatures higher than 60°C, and carbidic carbon and adsorbed oxygen were formed on the cobalt surface. After the surface is covered with adsorbed carbon and oxygen, no further dissociation of adsorbed CO occurs. Contrary to the dissociation of adsorbed CO, the deposition of carbon by the concerted Boudouard reaction continues on the carbidic carbon-deposited surface. The deposition of carbon increases... 

However, it must be borne in mind that in previous work, H2 did not react with a triangular array of O ions to form OH" ions (354). If such a reaction with H2 occurred, then the O" ions would no longer be available for Oj formation. Moreover, the reaction of pairs of O ions with oxygen should lead to pairs of O J ions which would have an abnormal EPR spectrum if they can be seen at all. In fact, the g tensor is as expected for isolated OJ ions. The CoO-MgO system behaves as CaO for the formation of Oj, i.e., via invisible O ions. The ozonide ions characterized by a three-g-value EPR signal (2.0025, 2.012, 2.017) do not exhibit any superhyperfine interaction with cobalt nuclei, suggesting that they are adsorbed on Mg2+ ions (110). Depending on the system (MgO, CaO, CoO-MgO) and the experimental conditions, the ozonide ion Oj disappears irreversibly between 25° and 130°C. In the case of MgO (333,334), OJ ions are formed when O J ions are destroyed, whereas for CaO (158) and CoO-MgO (110) the evidence is not clear. 

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