CO adsorption on palladium model catalysts:: XPS Pd-Al2O3 interaction study

The metal-substrate interaction (MSI) represents one of the most important effects determining the properties of supported catalysts. It is expected to be one of the driving forces of the size effect in catalysis. In this work we investigated the MSI by X-ray photoelectron spectroscopy (XPS) in the case of small Pd particles deposited on gamma -and cc-alumina substrates; We compared the binding energy and initial state variations as a function of Pd coverage. The initial state has been found to be shifted to higher positive values for a, more strongly interacting substrate (gamma -Al2O3), whilst for the inert-like sapphire substrate the MSI was less important. The initial state shift value was associated with the electron transfer in the substrate clusters direction. It was shown that the substrate-metal charge transfer could be responsible for partial CO dissociation on gamma -Al2O3 supported Pd particles. (C) 2000 Elsevier Science B.V. All rights reserved.