Carbon dissolution in palladium alloy catalysts

Palladium catalyzed alkyne and alkene hydrogenations are one of the most important processes of the chemical industry. Recently we have shown that carbon dissolves in the top few layers of palladium (forming a surface PdC phase) during the initial stage of alkyne hydrogenation enabling selective operation, whereas during unselective alkyne hydrogenation and alkene hydrogenation carbon dissolution was strongly suppressed or not observed at all. In this study we evaluated experimentally and theoretically whether alloying palladium with a second metal has an effect on the dissolution of carbon. We have found that Pd3Ni clearly prefers to dissolve carbon, but alloying Pd with Ag or Au strongly hinders the formation of subsurface carbon. The effect of alloying and of subsurface carbon on the properties of surface and subsurface hydrogen will be discussed, as well