Ammonia, adsorption binding energies

CI2 evolution reaction, 38 56 electrochemical desorption, 38 53-54 electrode kinetics, 38 55-56 factors that determine, 38 55 ketone reduction, 38 56-57 Langmuir adsorption isotherm, 38 52 recombination desorption, 38 53 surface reaction-order factor, 38 52 Temkin and Frumkin isotherm, 38 53 real-area factor, 38 57-58 regular heterogeneous catalysis, 38 10-16 anodic oxidation of ammonia, 38 13 binding energy quantification, 38 15-16 Haber-Bosch atrunonia synthesis, 38 12-13... 

Although no high resolution studies have been reported for ammonia interaction with iron surfaces, two main states of adsorption were recognized. At 80 K adsorption is entirely molecular with a characteristic N(ls) binding energy of 400 eV, but on warming the adlayer to 290 K the N(ls) intensity is mainly at 397 eV, typical of chemisorbed nitrogen adatoms with only a small contribution at 400 eV. 

The variations of acidic properties in the surface layers and in the bulk solid catalysts after calcination, reduction, or coking were examined by pyridine Nls XPS [4,7] and by the pyridine infrared adsorption techniques, respectively. This provides a means to compare the changes in the characteristic BrBnsted and Lewis acidity functions after those treatment conditions. First of all, TPD of ammonia revealed that both coked and regenerated samples exhibited much decreased acidity as compared with either calcined or reduced samples before the reaction of n-heptane conversion in either N2 or H2 stream [7]. The adsorption of pyridine may cause further perturbation to the Pt4+ or Pt 2+ species in the zeolite as indicated by the increase in binding energies of Pt3d5/2 electrons, as shown in Table 3 and Figure 4,... 

Tab. 22.2 Proton transfer energy, A pj, deprotonation energy, E yp, hypothetical binding energy of NH4 on the deprotonated zeolite surfaces, E p(SH ), and energy of ammonia adsorption, ad( 3) ( J for Bronsted sites in different zeolite frameworks [13].

Grunze M, Brundle C, Tomanek D (1982) Adsorption and decomposition of ammonia on a W (110) surface photoemission fingerprinting and interpretation of the core level binding energies using the equivalent core approximation. Surf Sci 119 133-149... 

Nitrogen adsorption has been especially studied on iron, which is the basis of the industrial catalyst for ammonia synthesis. This catalytic reaction is now relatively well understood [21]. The main function of iron is to activate the very stable N2 molecule by dissociative adsorption. Results in Table 3 show that the Fe-N binding energy is approximately the same on the three main low-index planes. However, the rate of N2 dissociation decreases by many orders of magnitude when going from Fe(lll), the most active for ammonia synthesis, to the less active Fe(llO). 

This can be done for all partial reactions and the onset potential as a function of the adsorption energy of N for the limiting reactions step as seen in Figure 18.11. On transition metal nano-clusters of selected catalyst, it is in principle possible to produce ammonia electro-chemically at an overpotential of —0.5 V, see Ref. [113] for details. A search for new catalysts using this surface termination is only necessary to calculate the adsorption energies of N and search for pure metals, nano-clusters alloys, or possibly nitrides which bind N by -1.1 eV. 

---