Chloride-induced morphology transformations of the Cu(110) surface in dilute HCl.

Morphological changes of a bare Cu(110) substrate in 10 mM HCl aqueous solution have been studied using cyclic voltammetry (CV), electrochemical scanning tunneling microscopy (EC-STM), and reflectance anisotropy spectroscopy (RAS). At cathodic potentials more positive than the hydrogen evolution reaction, a bare copper surface (1 × 1) structure is found by EC-STM. At anodic potentials more negative than the copper(II) dissolution reaction, a furrowed structure is found. The governing factor that rules Cu(110)-Cl interface processes is discussed as an interplay among Cl(-) adsorption/desorption, the dynamic rearrangement of the surface atoms on the substrate, and strain in order to reduce the surface energy. The information provided by EC-STM and RAS complements that of CV, supplies detailed information on the surface morphology, and correlates peaking Faraday currents to structural modifications. Furthermore, RAS and EC-STM show changes in the surface appearance in a potential range where no specific charge transfer is observed. CV indicates that the Cu(110) surface chemistry compares much better to that of amorphous Cu than to that of the more stable (100) and (111) surfaces, respectively.