Dissociative adsorption of hydrogen on strained Cu surfaces

The adsorption and dissociation of hydrogen on strained clean and oxygen-covered Cu surfaces have been studied by calculations based on density functional theory within the generalized gradient approximation. On all surfaces we find an upshift of the surface d-band center upon lattice expansion. Still there is no general trend in the hydrogen adsorption energies at the high-symmetry sites and the dissociation barrier heights as a function of lattice strain for the low-index Cu surfaces in contrast to the predictions of the d-band model. It turns out that the adsorbate-induced change of the Cu local d-band density of states has to be taken into account in order to rationalize these results. As far as the oxygen-precovered Cu(1 0 0) surface is concerned, the strain-induced change in the hydrogen adsorption energies and dissociation barriers can simply be related to the increased hydrogen–oxygen distance upon lattice expansion.