A new approach to well-defined, stable and site-isolated catalysts

A new concept to circumvent some of the problems that are hindering a rational metallic catalyst development is introduced. Investigation of conventional metal catalysts - which consist of supported metals, metal mixtures or alloys - is handicapped by the presence of a variety of active sites, their possible agglomeration, metal-support interactions as well as segregation of the components. In order to avoid most of the drawbacks, we employ well-defined, ordered and in-situ stable unsupported intermetallic compounds. Knowledge of the chemical bonding in the compounds and the defined neighbourhood of the active sites allows a rational approach to catalysts with excellent selectivity as well as long-term stability. The concept is demonstrated for the intermetallic compound PdGa, which is applied as catalyst for the selective hydrogenation of acetylene to ethylene.