Ethene adsorption and decomposition on the Cu(410) surface

The influence of open steps on the surface properties is shown by investigating the interaction of molecular ethene with Cu(410). We find a surprisingly low-temperature, site-selective chemistry at the strongly under-coordinated step sites. Ethene bonds either in a pi-bonded or in a di-sigma-bonded state or undergoes complete dehydrogenation. All pathways involve the low-coordination sites at the step, since the first species is partially stabilized with respect to low-Miller-index Surfaces, while the other two are observed only on Cu(410). When annealing the surface, dehydrogenation and transformation into the di-sigma-bonded moiety proceed, both processes being favored by faster heating rates. The so-generated carbon (presumably C(2) admolecules) decorates the step edges, thereby blocking the active sites for subsequent dissociation and permitting only pi-bonding of ethene. The dip de loss of carbon disappears ill high-resolution electron energy loss spectroscopy when annealing to room temperature, indicating that carbon moves to more coplanar or even to subsurface sites where it still influences the sin-face chemistry. The surface reactivity is recovered when heating the crystal to 900 K since C dissolves then deep enough into the bulk.