Sensitivity of catalysis to surface structure: The example of CO oxidation on Rh under realistic conditions

Using a combination of surface x-ray diffraction and mass spectrometry at realistic pressures, the CO oxidation reactivity of Rh(111) and Rh(100) model catalysts has been studied in conjunction with the surface structure. The measurements show that the presence of a specific thin surface oxide is crucial for the high activity of the Rh based CO oxidation. As this oxide is readily formed on all Rh facets, we conclude that the specific Rh crystal planes exposed during catalysis will not directly influence the reactivity. This is fortified by the very close similarity between the Rh(111) and the Rh(100) results.