Atom-Molecule Interactions on Transition Metal Surfaces: A DFT Study of CO and Several Atoms on Rh(100), Pd(100) and Ir(100)

Density functional theory (DFT) calculations have been performed to determine the interaction energy between a CO probe molecule and all atoms from the first three rows of the periodic table coadsorbed on Rh(100), Pd(100) and Ir(100) metal surfaces. Varying the coverage of CO or the coadsorbed atom proved to have a profound effect on the strength of the interaction energy. The general trend, however, is the same in all cases: the interaction energy becomes more repulsive when moving towards the right along a row of elements, and reaches a maximum somewhere in the middle of a row of elements. The absolute value of the interaction energy between an atom–CO pair ranges from about −0.40 eV (39 kJ mol−1) attraction to +0.70 eV (68 kJ mol−1) repulsion, depending on the coadsorbate, the metal and the coverage. The general trend in interaction energies seems to be a common characteristic for several transition metals. On the surface: Trends in the interaction energy between CO and all atoms from the first three rows of the periodic table coadsorbed on Rh(100), Pd(100) and Ir(100) surfaces have been studied. The results indicate that the strength of the interaction energy between CO and a coadsorbed atom on a certain catalyst surface is specific for the particular combination and the coverages of all the species involved (see picture for Rh; ML=monolayer).