Autocatalytic effect of Cu nano-islands on the reaction of water with the oxygen covered Cu(110) surface

We present a detailed STM study on the reactivity to water of the oxygen covered Cu(110) surface at 200 K. This reactive interaction is known to produce hydroxyls. We found that the hydroxyl chemical state is a key factor regulating further chemical reactions and causing a strong re-structuring of the surface. Parts of the hydroxyls are originally produced on the surface in the form of highly mobile copper–hydroxyl [Cu–OH] complexes. We demonstrate that interaction of the [Cu–OH] complexes with the substrate governs the surface restructuring. The hydroxyl complexes can dissociate either on step sites of the surface, incorporating Cu to the substrate and releasing hydroxyls (OHs) either, remarkably, condensate on the terraces shaping two-dimensional monoatomic height Cu islands possessing under-coordinated sites at their borders. We show that nucleation and growth of these nanometer scaled islands significantly enhance the surface reactivity towards water. Indeed, the Cu islands providing under-coordinated sites enhance water adsorption and furthermore produce a local effect favoring diffusion of the water molecules towards the more reactive sites.