Temperature- and pressure-dependent adsorption configuration of NO molecules on Rh(111) surface: A theoretical study

Understanding the behavior of NO molecules on Rh metal surfaces is necessary for gaining fundamental knowledge about catalytic chemistry and surface science. The present theoretical study details the configuration of NO molecules adsorbed on Rh(111) surface on the basis of density functional theory (DFT) calculations. The impact of coverage dependences on the adsorption/desorption energies is examined systematically: multiple configurations of NO adsorption structures are investigated with NO surface coverage from 0.06 to 0.75. A phase diagram for the various NO configurations with temperature and pressure is obtained by considering the adsorption equilibrium. Adsorption energies of NO molecules generally decrease with increasing surface coverage, reflecting the repulsive interactions between the adsorbed NO molecules. Microkinetic simulations for temperature-programmed desorption (TPD) spectra are performed. Simulated TPD spectra on the basis of the surface coverage-dependent desorption energies are in reasonable agreement with the experimental results.