Dissociative Adsorption N2 on Ruthenium Surfaces

The barrier for dissociation at the surface is much lower than that for dissociation in the gas phase, which for N2 would require about 9.8 eV (945 kJ mol ) and would lead to two free N radicals. The surface reaction offers an energetically much more 

Note that the dissociation proceeds with a much lower barrier on the stepped surface. As the structure diagrams show, at all stages in the dissociation the species are more strongly bound on the stepped surface, for reasons discussed in connection with Eq. (87). However, the transition state is most affected, because two N atoms are bound to four metal atoms in the transition state on a perfect surface, whereas that on the stepped surface consists of five metal atoms. As noted above, geometries in which atoms bind to different metal atoms are always more stable than when the two adsorbate atoms share one metal atom. Hence, dissociation is favored over step sites, and if a surface contains such defects they may easily dominate the kinetics. 

---