Interactions between co-adsorbed CO and H on a Rh(100) single crystal surface.

Co-adsorption of CO and H(2) on a Rh(100) single crystal surface has been studied by a combination of temperature programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS), low energy electron diffraction (LEED), and density functional theory (DFT) calculations. Exposure of CO to a hydrogen precovered surfaces at 150 K results in some displacement of adsorbed hydrogen and a layer with 0.67 ML H and 0.67 ML CO is obtained. A c(3 square root(2) x square root(2))R45 degree structure is formed with CO occupying bridge sites and hydrogen occupying partly bridge sites on the surface and partly octahedral subsurface sites, causing hydrogen to desorb at temperatures around 230 K.