Carbon monoxide chemisorption and disproportionation on thin palladium layers, supported by niobium and niobium pentoxide

Thermally programmed desorption technique has been applied to the investigation of "virgin" and repeated adsorption of carbon monoxide on Pd/Nb and Pd/Nb2O5/Nb systems. The desorbed products of the CO interaction with these surfaces, CO and CO2, were monitored with a quadrupole mass spectrometer. On the basis of presented results some of the observed differences between the metal- and oxide-supported active metal (Pd) have been ascribed to the morphological rather than to chemical (electronic) effects in these systems. The different excess kinetic energy dissipation of Pd atoms colliding with metallic or oxidic surface is considered to influence the initial growth of the Pd layer, resulting afterwards in a different morphology of the final Pd layers.