The Brønsted–Evans–Polanyi Relation and the Volcano Plot for Ammonia Synthesis over Transition Metal Catalysts

Abstract

Using density functional calculations we show that there is an essentially linear relationship between the activation energy for N2 dissociation and the binding energy of atomic nitrogen on a range of transition metal surfaces. This relation, known as the Brønsted–Evans–Polanyi relation, is further shown to depend on the structure of the active site. The consequences of the Brønsted–Evans–Polanyi relation in terms of the kinetics of the ammonia synthesis process under industrial conditions are discussed, and it is shown that the relation leads to a volcano-type dependence of the catalytic activity on the nitrogen heat of adsorption. The results show that density functional calculations can predict the relative catalytic activity of different transition metals.