Coverage of adsorbed nitrogen

It can be seen that from VA to VIII groups, the initial adsorption heat of nitrogen decreases and ammonia synthesis rate reaches a maximum value, and after that the rate goes down due to the reduction of surface coverage of adsorbed nitrogen. 

H2 on noble metal catalysts, platinum, and rhodium. Since one of the antibonding orbitals of NO bond is occupied by an electron, the N-O bond is weaker than the bond of CO. The rate of dissociative NO adsorption is generally faster than that of CO. Rhodium is more reactive than platinum. Therefore the rate of dissociative adsorption of NO is higher on Rh than on Pt, as is the steady-state coverage of adsorbed nitrogen atoms. 

The total amount of adsorbed nitrogen was determined by integration of the characteristic peaks. The maximum coverage of nitrogen (ca 1.5 at%) relative to the total XPS sampling depth corresponded to rather less than 0.1 monolayers it was achieved with the y-state. The a- and )3-states were, at the most, about half as abundant as the y-state based on the assumption of equal cross sections for all three states. 

The dissociation of N2 is a slow reaction step. It is suppressed by competitive adsorption of NH3 that blocks sites needed for nitrogen dissociation. Promoters, such as potassium, are added to enhance the rate of nitrogen dissociation and to weaken the interaction of NH3 with the catalyst surface. Reduction of the surface coverage of adsorbed NH3 enhances the overall rate of reaction, as indicated by the... 

In the following we consider nitrogen atoms adsorbed on a ruthenium surface that is not completely flat but has an atomic step for each one hundred terrace atoms in a specific direction. The nitrogen atoms bond stronger to the steps than to the terrace sites by 20 kj mok. The vibrational contributions of the adsorbed atoms can be assumed to be equal for the two types of sites. (Is that a good assumption ) Determine how the coverage of the step sites varies with terrace coverage. 

Less, but still significant, information is available on the surface chemistry of other nitrogen oxides. In terms of N20, that molecule has been shown to be quite reactive on most metals on Rh(110), for instance, it decomposes between 60 and 190 K, and results in N2 desorption [18]. N02 is also fairly reactive, but tends to convert into a mixed layer of adsorbed NO and atomic oxygen [19] on Pd(lll), this happens at 180 K, and is partially inhibited at high coverages. Ultimately, though the chemistry of the catalytic reduction of nitrogen oxide emissions is in most cases controlled by the conversion of NO. 

Isotopic Tracing with l NO. To trace out the dynamics of nitrogen incorporation into the products under conditions where the surface coverage by adsorbed NO remains constant, experiments... 

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