Structure and reactivity of a model catalyst alloy under realistic conditions

Abstract

Using a combined experimental and theoretical approach, we show that a thinRhO2 oxide filmforms on a Pt25Rh75(100) surface at elevated oxygen pressures and temperatures prior to the bulkoxidation. By the use of in situ surface x-ray diffraction under realistic COoxidation reaction conditions, we show that the onset of the growth of thinRhO2 oxide film coincideswith an increase in CO2 production. During the reaction, the consumed oxide film is continuouslyre-grown by oxygen in the gas phase. Our theoretical results strongly suggestthat the CO adsorbs on the metallic substrate but reacts with the O in theRhO2 oxide film at theborder between the RhO2 oxide film and the metallic substrate. This scenario could explain the experimentalobservations of oxidation reactions on other late transition metal surfaces as well as ontheir corresponding nanoparticles under realistic conditions.