Steps Accelerate the Formation of Rhodium Surface Oxide

The oxidation of rhodium surfaces has wide-ranging impacts on heterogeneously catalyzed reaction mechanisms. Not only is rhodium itself catalytically active, but it also serves as a robust model system for understanding the oxidation chemistries of platinum-group metals or late transition metals in general. The chemical speciation of oxygen on rhodium surfaces is reasonably well understood, and this knowledge can be used to discover how structural changes affect the oxygen speciation. Herein, we report our findings for the oxidation of a bifaceted Rh(111)/(322) crystal that show that when the surface is oxidized, the steps on the (322) facet hinder the formation of crystalline surface phases at low temperatures and accelerate surface oxide formation at elevated temperatures. The narrow terraces used provide insight into how highly defective surfaces, like nanoparticles, will behave under strongly oxidizing conditions.