TPD Study of Carbon Monoxide Interaction with Pd/Nb Bimetallic System

Abstract

Chemisorption properties of thin films of Pd evaporated onto Nb recrystallized-foil surface have been studied by temperature-programmed desorption (TPD) and by measurement of the work function changes (WFC) at room temperature. TPD results indicate two states of CO adsorbed in dependence 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 attributed to bulk Pd. WFC data show negligible change of the work function after deposition of small amounts of Pd onto a clean Nb surface. With increasing amount of Pd, ∆ϕ rises and reaches a saturation value. Adsorption of CO onto Pd/Nb surface caused the work function increase at all coverages of Pd deposited.