A RAIRS, TPD and DFT study of carbon monoxide adsorption on stepped Rh(553)

The adsorption and desorption of carbon monoxide on Rh(553) was studied using temperature-programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS), and density functional theory (DFT) calculations. The results are discussed with respect to the previously reported results on the Rh(111) surface. TPD of carbon monoxide from Rh(553) is very similar to the TPD from Rh(111). This observation is confirmed by DFT calculations, which show that the adsorption geometries and adsorption energies are only slightly different on the two surfaces. Infrared spectroscopy shows that, at low coverages, on-top adsorption sites on the steps and on the terraces are occupied first. With increasing CO coverage also bridge sites on the steps are occupied, while bridge and hollow sites on the terraces are only occupied at the highest CO coverages. DFT calculations support the assignments of the IR peaks to the different adsorption sites.