XPS, TDS and static SIMS studies of binary Pd/Al system properties: correlation between Pd-Al bimetallic interaction and CO adsorption

Pd adlayers, prepared by vacuum evaporation onto a pure polycrystalline Al surface, exhibited a strong interaction with Al atoms resulting in formation of a Pd-Al alloy of a noble metal-like electronic structure. The shifts of the Pd 3d core levels and the Pd 4d-band centroid toward higher binding energies due to bimetallic bond formation were observed. The CO TDS spectra consisted of two desorption peaks, both lying lower than the one typical for a Pd foil, indicating distinct weakening of the Pd-CO chemisorption bond. Partial CO dissociation on the Pd/Al surface during adsorption/desorption cycles, accompanied by CO2 and H2O production, was observed. CO dissociation caused creation of Pd-C and Al-O chemical bonds on the Pd/Al surface resulted in weakening of the Pd-Al bimetallic bond.