Factors Governing the Stability of Dilute Alloy Catalysts under Reaction Conditions

Dilute alloy catalysts, typically consisting of a small amount of catalytically active dopant metal dispersed in a more inert host metal, are a promising class of materials that can potentially circumvent the scaling-relation limitations of conventional catalysts. Although recent efforts have succeeded in discovering unique chemistries that can be catalyzed by dilute alloy catalysts, relatively little attention has been given to the stability of these catalysts under reaction conditions. In this contribution, we study the stability of different dilute alloy catalysts as a function of reaction conditions. We show that the identity of the adsorbate and the miscibility of the alloying metals are two important factors that govern the thermal stability of dilute alloy catalysts. We show that adsorbates that bind more strongly to the active sites exhibit an improved stability by pinning the dopant atoms at the surface, while the immiscibility between the dopant and host metals mitigates the dissolution of surface dopant atoms into the host-metal bulk, thereby preserving the surface dopant atoms.