On-surface oxygen

Figure 9. Effect of burnoff on surface oxygen content natural graphite NG7 [391.

Quantitative experiments have been performed to find the stoichiometry of oxygen complexes on surfaces. Oxygen also adsorbs reversibly on a Fe(II) porphyrin attached to the imidazole groups of a silica gel that is adequately treated to give a 1 1 stoichiometry of the Fe-02 adduct (320). 

Fig. 5.2. Computed (DFT-GGA) binding energies Eb(0) for on-surface oxygen chemisorption into the most stable hollow sites of the basal surface of the late 4d TMs (Ru = hep site, Rh/Pd/Ag = fee site) and employing (2 X 2) surface unit-cells (the lines are only to guide the eye). The energies are given with respect to the theoretical O2 binding energy, cf. (5.1), while the upper horizontal dotted line indicates the zero level, if the experimental O2 binding energies were used (after [18])...

O—C02) are formed together with carbonate ions in some cases. The interaction is believed to result from the chemisorption of C02 in a bent configuration on surface oxygen atoms. Since the stable species are not formed on the monovalent cation zeolites, the divalent cations must promote the chemisorption. Furthermore, since the frequencies observed are a function of the exchanged cation, the adsorption must occur in the vicinity of the cations. Adsorption of water and ammonia removed the 1575 and 1380 cm-1 bands and formed bands at 1620 and 1450 cm"1, respectively. The carbonate bands were restored by evacuation at 300°C. Benzene had no effect. The observations are believed to reflect hydrogen bonding. 

Active oxygen species, such as superoxide (Oj), are formed on surface oxygen... 

Bonding of the aryl groups on surface oxygen atoms. 

The negatively charged adsorbed species of CO react with H to form [CHO] groups which are adsorbed on surface oxygen ions. The [CHO] group adsorbed on oxygen ion becomes the same structure as the formate group, hence the IR spectra tire the same as those for formate. 

The vertical change of positions for both the partners should satisfy the numerical relation between Do and Di2- However, the simple operation on the Cu 0 Cu chain provides entirely different physical meanings. Therefore, physical constraints should be necessary for the numerical solutions. For instance, the on-surface oxygen should be ruled out for the fully developed surface oxidation. The on-surface oxygen neither produces protrusions in the STM images nor expands the first interlayer spacing. 

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