Dissociation and recombination rate constants for N2 on Cu and Ni group transition metal surfaces

We report dissociation and recombination reaction rate constants for N2 on the fcc(1 1 1) surfaces of Ni, Pd, Pt, Cu, Ag and Au from molecular dynamics simulations employing our normalized bond index-reactive potential functions. The Arrhenius pre-exponentials for recombination of N2 on these surfaces are three to four orders of magnitude greater than the dissociation pre-exponentials, which is similar to results we obtained for CN. On the series of metals considered herein, the reaction energetics favor dissociation on the more active metals and favor recombination on the least active metals. The recombination of N2 on gold and silver is diffusion controlled. The large differences in the dissociation/recombination pre-exponentials express the tendency of the reaction entropy to favor the recombination on the surfaces investigated. We discuss the low sticking probability of N2 in terms of our previous modeling of adsorption/desorption processes.