Oxygen adsorbed magnesium

Cordischi et al. (110) have extended the studies on the CoO-MgO system by impregnating magnesium hydroxide with low contents of CoO (0.05 5 atom % Co) and showed unambiguously that oxygen is adsorbed on Co3 + at 77 K by the observation of a superhyperfine structure due to interaction of the unpaired electron of 02 with the nuclear spin of Co (1 = ). At higher temperatures of adsorption, the 02 ion is adsorbed on Mg2+ in agreement... 

Magnesium oxide may be expected to function as an active catalyst for CO2 utilization since CO2 is easily chemisorbed on MgO [1-3]. Most works so far reported on this adsorption system were carried out above the room temperature, and recent works have demonstrated the occurrence of oxygen isotope exchanges between adsorbed species and surface 0 [4-6]. However, dynamic behaviors of adsorbed species, especially below the room temperature, are still open to question. 

Nanocrystalline MgO also has a large capacity for adsorbing acid gases such as S02, C02, HC1, HBr, and S03 at near stoichiometric proportions. Work by Klabunde has demonstrated that nanocrystalline magnesium oxide has an enhanced surface reactivity over that anticipated from surface area alone. Nanocrystalline MgO chemisorbed 6 molecules of S02 per nm2, whereas larger microcrystalline MgO only chemisorbed 1.8 molecules per square nanometer (Stark and Klabunde, 1996). The proposed mechanism for the difference in adsorption capacities is due to a monodentate-type adsorption mechanism of S02 via the sulfur atom in the instance of nanocrystalline MgO, whereas microcrystalline MgO favors a bidentate adsorption mode through sulfur and an oxygen atom. 

In Nature (on membranes of chloroplasts) water is oxidized by the four-electron mechanism and the life-time of chlorophyll can be as long as one day. In a model octane/water system, oxygen evolution occurs also during several hours. This is indirect evidence in favor of a many-electron reaction. Therefore we shall consider a four-electron mechanism of water oxidation sensitized by chlorophyll adsorbed at the oil/water interface proposed by Volkov [81]. It was shown above that the interface is the most likely site for the water photooxidation reaction. Thus it is assumed that water can be oxidized by a reaction complex adsorbed at the interface that consists of a hydrated oligometer of chlorophyll, a hydrophilic electron acceptor and hydrophobic proton acceptor [81,82,86]. The water in the reaction complex is linked coordinatively with the magnesium of one of the chlorophyll molecules, by hydrogen bonds with the carbonyl group of another chlorophyll molecule, and with the phenol anion also... 

Marine environments typically have high RH, as well as salt rich aerosols. Studies have shown that the thickness of the adsorbed layer of water on a zinc surface increases with percent RH and that corrosion rates increase with the thickness of the adsorbed layer. There also seems to be a finite thickness to the water layer that, when exceeded, can limit the corrosion reaction due to limited oxygen diffusion [4]. However, when metallic surfaces become contaminated with hygroscopic salts their surface can be wetted at a lower RH. The presence of magnesium chloride (MgCy on a metallic surface can make a surface apparently wet at 34 percent RH while sodium chloride (NaCl) on the same surface requires 77 percent RH to create the same effect [5]. 

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