Improvement of intermetallic catalysts using surface segregation of third elements demonstrated by adding Cu to CoGa for selective hydrogenation of propyne

Intermetallic compounds can be novel catalysts due to unique atomic-ordered arrangements and electronic structures. However, their elemental set, composition, and crystal structure cannot be freely selected, which limits the tunability of catalytic properties. In this study, we demonstrated an improvement in catalytic properties by adding a third element to intermetallic catalysts using selective hydrogenation of propyne by CoGa with Cu addition as a model reaction and catalyst. The selectivity was drastically improved by 5 %Cu addition. The surface segregation of Cu was revealed and considered to result in an ensemble effect for the selectivity improvement. The addition of NiGa to Cu does not result in segregation. Since Cu-Ni is miscible, but Cu-Co is immiscible, the third element should likely be immiscible with one component of intermetallic catalysts to utilize a segregation effect for improving catalytic properties. • Adding a small amount of Cu significantly improved the selectivity of propene. • Cu atoms segregated to the surface of CoGa, leading to the site-isolation effect. • The Cu segregation was not observed in NiGa with Cu. • Besides the low surface energy, the immiscibility of Cu with Co was critical.