Quantification of lateral repulsion between coadsorbed CO and N on Rh(100) using temperature-programmed desorption, low-energy electron diffraction, and Monte Carlo simulations

Temp. programmed desorption of CO coadsorbed with at. N on Rh(100), reveals both long- and short-range interactions between adsorbed CO and N. For CO desorption from Rh(100) at low coverage we find an activation energy Ea of 137+-2 kJ/mol and a preexponential factor of 1013.8+-0.2 s-1. Coadsorption with N partially blocks CO adsorption and destabilizes CO by lowering Ea for CO desorption. Destabilization at low N coverage is explained by long-range electronic modification of the Rh(100) surface. At high N and CO coverage, we find evidence for a short-range repulsive lateral interaction between COads and Nads in neighboring positions. We derive a pairwise repulsive interaction wCO-NNN=19 kJ/mol for CO coadsorbed to a c(2*2) arrangement of N atoms. This has important implications for the lateral distribution of coadsorbed CO and N at different adsorbate coverages. Regarding the different lateral interactions and mobility of adsorbates, we propose a structural model which satisfactorily explains the obsd. effects of at. N on the desorption of CO. Dynamic Monte Carlo simulations were used to verify the exptl. obtained value for the CO-N interaction, by using the kinetic parameters and interaction energy derived from the temp.-programmed desorption expts. [on SciFinder (R)]