THE SURFACE SCIENCE OF HETEROGENEOUS CATALYSIS

The development of a high pressure cell that can be incorporated into ultrahigh vacuum chambers permitted surface science studies of active catalysts. Model catalysts, usually single-crystal surfaces of similar to 1 cm(2) surface area, can be used to study important catalytic reactions ranging from hydrocarbon conversion over platinum to ammonia synthesis over iron. The new concepts, or phenomena, uncovered by the surface science investigations of heterogeneous catalysis of these model systems include: (1) high reaction rates and strong bonding at defects and on rough surfaces; (2) adsorbate-induced restructuring of metal surfaces that control the reaction rates; (3) the presence of a strongly chemisorbed overlayer which covers much of the active metal surface; (4) the bonding and reaction rate modifying influence of coadsorbates; and (5) the unique activity of certain oxide-metal interfaces.