Surface Interactions in Pd-Nb System and Their Relation to Basic Questions and Practical Catalysis

Abstract

Room temperature adsorption-desorption properties of Pd overlayers of various thicknesses were studied by thermal desorption spectroscopy of carbon monoxide. Pd overlayers were deposited on clean and oxidized Nb foil (NbOx/Nb). Adsorption properties of Pd overlayers deposited on clean Nb at temperature 350-400 K were not influenced by annealing in the temperature range 400 K to 600 K. Annealing above this temperature caused the decrease in the area of the Pd surface. It became probably smoother, exhibiting lower number of adsorption sites for CO. Non-annealed Pd overlayers deposited on the oxide carrier (NbOx/Nb) at temperatures between 350 and 400 K possessed the same adsorption capability as Pd deposited directly on Nb. Pd atoms thus neither massively penetrated into the oxide layer nor were encapsulated by NbOx.