Adsorption of nitrogen on potassium promoted Fe(111) and (100) surfaces

摘要: Dissociative nitrogen adsorption through N2 ⇌ N2,ad → 2Ns is the rate limiting step in ammonia synthesis over iron catalysts. This model study deals with “promoter” action of potassium by studying influence preadsorbed K on energetics and kinetics molecular atomic Fe(111) Fe(100). The heat locally increased to about 11 kcal/mole vicinity an adsorbed atom, which phenomenon simultaneously lowers activation barrier for dissociation. As a consequence effective sticking coefficient dissociative markedly increased. effect less pronounced than Fe(100) so that difference activity observed K-free surfaces eliminated. increase energy attributed enhanced electron density substrate (due charge transfer from K) enables more “backbonding” contribution bond.