ROLE OF ENERGY-DISSIPATION AND SURFACE MOBILITY IN HETEROGENEOUS CATALYSIS BY METALS

The fundamental role of excess energy dissipation and of surface speci es mobility, both in the preparation of model metallic catalysts (bime tallic catalysts, bimetallic oxide-supported catalysts), and in the ac tivation of reactant molecules on the catalyst surfaces (single crysta ls, bimetallic and bimetallic oxide-supported catalysts) are discussed . A generalized model of surface interactions is proposed which satisf actorily explains the trapping of particles from the gas phase at the atomic steps and recovery of the trapping sites due to migration of th e trapped species towards flat terraces. Higher probability of encount er of these species with other reactants on flat terraces and easier d esorption of the reaction products from there in comparison with the b ound state at the edges of atomic steps can be expected. Results of FI M and FEM studies of Pt, Dy-W, Pd-W and Pd-Mo systems are used to illu strate selected features of the proposed general model.