AbstractsChemistry

The interaction between hydrogen and a transition metal surface is an important aspect of many chemical processes, in particular heterogeneous transition metal catalysts. Density functional theory calculations are used here to study the interaction of a hydrogen adatom with open facets of 14 transition metals, either FCC(100) or BCC(100) surfaces. Potential energy surfaces are generated representing the variation of the binding energy of atomic hydrogen over the surface unit cell. On Ag, Au and Cu the adsorption of hydrogen is endothermic with respect to gas phase H2 but on the rest of the metals it is exothermic. The activation energy for hydrogen diffusion over the surface is extracted from the calculated results. A wide variation in activation energy is found, from 0.02 eV for Pd(100) to 0.36 eV for W(100). The effect of metal atom relaxation was assessed by comparison with calculations using frozen surfaces.