Low oxygen coverage

As usual, things become more complicated when studied in detail. Note that for 0/W(l 10) 0 varies with 6 the situation is shown more fully in Fig. XVIII-15. The authors speculate that variations in Dq and E have to do with a p(2 x 1) structure at low oxygen coverage, with O atoms occupying alternate rows of W atoms, the empty rows becoming occupied above 0 = 0.5. The consequence is that O—O interactions shift from being mostly attractive to being in part repulsive. 

The selectivity depends strongly on the oxygen coverage. At low oxygen coverages the selectivity is much lower than at high coverages (cf. Fig. 5.15). 

Scheme 1. Proposed mechanism for the partial oxidation of 2-propyl surface species on O/Ni(100) at low oxygen coverages. A similar mechanism is likely to operate during the catalytic conversion of alkanes on substoichiometric nickel oxides.

As shown on Cu(llO) [109], this reaction occurs only for low oxygen coverage, the oxygen-saturated surface being totally inactive. A typical curve in Figure 14 shows that, for 0, < 0.1 the slope of the curve is 2, indicating that, as expected from reaction (1), 20H are formed per adsorbed... 

In the precursor phase, or at very low oxygen coverage, oxygen deposits randomly into the Ctv hollow site to form a B5O cluster. This cluster can be expressed as ... 

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