TPD STUDY OF CARBON-MONOXIDE INTERACTION WITH PD NB BIMETALLIC SYSTEM/

Chemisorption properties of thin films of Pd evaporated onto Nb recrys tallized-foil surface have been studied by temperature-programmed deso rption (TPD) and by measurement of the work function changes (WFC) at room temperature. TPD results indicate two states of CO adsorbed in de pendence on the thickness of the palladium layer. The low temperature state (330 K) occurs at low Pd coverages (about one monolayer). Second state, occurring at slightly higher temperature (370 K), is attribute d to bulk Pd. WFC data show negligible change of the work function aft er deposition of small amounts of Pd onto a clean Nb surface. With inc reasing amount of Pd, DELTAphi rises and reaches a saturation value. A dsorption of CO onto Pd/Nb surface caused the work function increases at all coverages of Pd deposited.