Nickel oxide preadsorbed oxygen

Fig. 17. Thermograms recorded during the adsorption of doses of oxygen at the surface of nickel-oxide samples containing preadsorbed oxygen, the cold trap being cooled (A) or not cooled (B) (71). 

Thermochemical Cycles Testing the Formation of Gaseous (Cycle 1) or Adsorbed (Cycle 2) Carbon Dioxide by the Interaction of Carbon Monoxide with Oxygen Preadsorbed on Gallium-Doped Nickel Oxide ... 

Fig. 26. Differential heats of interaction of carbon monoxide at 30°C with a sample of gallium-doped nickel oxide, containing a limited amount (0.4 cm3 02 gm l) of preadsorbed oxygen.

Fig. 29. Differential heats of interaction of carbon monoxide, at 200°C, with samples of nickel oxide containing excess oxygen, preadsorbed rapidly (A) or slowly (B).

Sequence II O2—CO. Oxygen is first adsorbed on NiO(250) at 30°C. The sample is then evacuated at 30°C. (amount of irreversibly adsorbed oxygen, 1.9 cc. per gram), and carbon monoxide is adsorbed at the same temperature (Figure 3). The electrical conductivity of nickel oxide containing preadsorbed oxygen 1.8 X 10 5 (ohm cm.)"1 decreases during the adsorption of CO, and at the end of the adsorption, is identical to the conductivity of the pure oxide. Moreover, carbon dioxide is condensed in the cold trap. This shows that all ionized species are transformed into neutral species at the end of the interaction. 

Figure 3. Adsorption of carbon monoxide on nickel oxide containing preadsorbed oxygen...

In the second series of experiments, the exchange of oxygen between adsorbed carbon monoxide and the lattice anions was followed at room temperature, either carbon monoxide (64) or nickel oxide (65) being labeled by 0. When the pressure of carbon monoxide is 80 torr, 20% of surface anions are exchanged at room temperature (64). The extent and the rate of this reaction are not modified if oxygen is preadsorbed on the sample before the exchange experiment. It has already been shown from the infrared absorption spectra (60) that no carbon monoxide is adsorbed irreversibly as CO on the surface cations of an... 

The reactivity of carbon dioxide toward oxygen was also studied (25, 66). First, carbon dioxide was adsorbed on nickel oxide containing preadsorbed oxygen. The black color and the high electrical conductivity of the sample remain unaltered (25). However, a reaction does occur since a subsequent adsorption of carbon monoxide produces a desorption of carbon dioxide, while adsorption of carbon monoxide is impossible on a sample precovered by carbon dioxide (25). It is believed that... 

Interaction between oxygen and carbon monoxide preadsorbed on NiO(10 Li)(250°) produces C03-(ads) ions, as in the case of all other samples. Thermochemical cycles 4 and 5 (Table XV) show, moreover, that the subsequent conversion of the complex ions by carbon monoxide yields carbon dioxide which remains partially adsorbed. Reaction mechanism II is therefore also probable on lithium-doped nickel oxides. 

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