ON THE REACTIVITY OF 2D PD SURFACE ALLOYS OBTAINED BY SURFACE SEGREGATION OR DEPOSITION TECHNIQUE

Two-dimensional Pd surface alloys can be obtained by two different methods: either by surface segregation or by deposition followed by controlled annealing. For a similar Pd surface concentration, Pd-Ni samples, prepared by these two ways, exhibit similar activity towards the hydrogenation of 1,3-butadiene and are more effective than pure Pd. Different UHV techniques allow us to think that the same catalytic behaviour is due to the same chemical composition and atomic arrangement at the very surface. Moreover, XPS measurements show similar electronic properties of the active site which might be a Pd pair modified by surrounding Ni atoms.