Pd–Ni nanoparticles: segregation and reactivity for the 1,3-butadiene hydrogenation reaction

A Monte-Carlo (MC) simulation has been employed to study the coordination of surface atoms in hydrogen-covered 2406-atom Pd1Ni99 and Pd5Ni95 nanoparticles. For both systems, Ni is found to segregate to the surface. It has been found that, for a full monolayer coverage of hydrogen, the average number of surface Pd neighbour atoms per surface Ni atom, 〈nNi–Pd〉, for Pd5Ni95 alloy surface is 6 times larger than the corresponding number 〈nNi–Pd〉 for the Pd1Ni99 alloy. The surface coordination in the alloys has been shown to explain qualitatively the experimentally observed increase in activity of Pd5Ni95 alloy over Pd1Ni99 alloy for the 1,3-butadiene hydrogenation reaction.