Study of CO interaction with alumina-supported Pd particles

Anomalous effects such as the enhanced sticking probability of CO and O-2 and the partial CO dissociation were measured on small Pd particles deposited on gamma-alumina. Recently, a dependence of the sticking coefficient on the substrate has also been reported on Pd/(0001) alpha-alumina but no dissociation has been observed in this case. We present a detail study of CO adsorption/desorption and catalytic reaction properties for a series of alumina substrates. Particularly, we used alpha-alumina of surface orientations (0001) and (<1(1)over bar 02>). Before the Pd deposition, the substrates were exposed to annealing at different temperatures in vacuum and in the air. The adsorption and reaction parameters of Pd particles change with crystallographical structure and stoichiometry of the substrate surface, essentially due to the effect of reactants diffusion over the substrate.