).
As supported PtxNi1-x catalysts are used for hydrogenation reactions, it seemed necessary to assess the surface composition of the reduced samples. To approach the usual reduction conditions we applied in situ reduction in a reaction chamber (1 mbar H2 up to 500°C) placed in ultra high vacuum recipient (UHV: 10-9 to 2x10-10 mbar). All ion scattering spectroscopy measurements were performed in UHV. Charging of the samples was avoided by electron bombardment (5 eV). The variation of the surface composition was determined after subsequent sputtering, thermal treatment at 500°C and during oxygen adsorption. A comparison with previous results of surface compositions of binary alloys (polycrystalline foils and single crystals PtxNi1-x) is given.
Corresponding author: P. Varga (varga).