Abstract

The oxidation of bimetallic alloy nanoparticles comprising a noble and a nonnoble metal is expected to cause the formation of a single-component surface oxide of the nonnoble metal, surrounding a core enriched with the noble metal. Studying the room temperature oxidation of Au–In nanoparticles, we show that this simple picture does not apply to an important class of bimetallic alloys, in which the oxidation proceeds via predominant oxygen diffusion. Instead of a crystalline In₂O₃ shell, such oxidation leads to an amorphous shell of mixed Au–In oxide that remains stable to high temperatures and whose surface layer is enriched with Au. The Au-rich mixed oxide is capable of adsorbing both CO and O₂ and converting them to CO₂, which desorbs near room temperature. The oxidation of Au–In alloys to a mixed Au–In oxide shows significant promise as a viable approach toward Au-based oxidation catalysts, which do not require any complex synthesis processes and resist deactivation up to at least 300 °C.