Building of Complex Catalysts on Single-Crystal Surfaces

Combined catalytic reaction and surface science studies using small area metal single crystal surfaces have shown these systems to be excellent model catalysts. In order to investigate more complex, multicomponent catalysts, other metals, oxides, chlorine, and sulfur were deposited from the vapor phase in controlled concentrations on the metal single crystals or polycrystalline foils to investigate their functions as structure or bonding modifiers. From studies of several of the complex catalyst systems (Pt/Au, Pt/Al2O3, Pt/Al2O3/Cl, Fe/Al2O3, Fe/Al2O3/K, Pt/Re, Pt/Re/S, Mo/S, Mo/Co/S), the molecular ingredients of their catalytic performance have been identified. These are the a) need for surface roughness; b) structural stabilization of rough surfaces; c) the presence of a strongly chemisorbed overlayer that causes surface restructuring; d) bonding modifier cooadsorbates; 3) active oxide-metal interfaces and f) active bimetallic interfaces.