Segregation of co-adsorbed species: Hydrogen and carbon monoxide on the (111) surface of rhodium

Abstract
The co‐adsorption of CO and H2 on Rh(lll) at low temperature (∼100 K) has been studied using thermal desorption mass spectrometry (TDS) and low energy electron diffraction (LEED). The probability of adsorption of CO on rhodium pretreated with hydrogen has been found to vary nonlinearly with the amount of hydrogen on the surface. In addition, the effect to surface hydrogen on the CO LEED patterns indicates near complete segregation of hydrogen and CO. These results can be explained qualitatively in terms of a strong repulsive CO–hydrogen interaction and a mobile precursor model of CO adsorption.