Palladium dispersion was determined by H2 pulsed chemisorption
measurements at 100 C using a Micromeritics AutoChem II
2920 apparatus. Before analysis, the sample was treated at
200 C in H2 for 2 h (3 C/min) and then in Ar at 400 C for 2 h
(10 C/min). The dispersion (D) defined as the fraction of palladium
at the surface, D = Pds/Pdtotal, was calculated with the assumption
of one H atom per surface Pd