Scanning Tunneling Microscopic Study with Atomic Resolution of the Dissolution of Cu(100) Electrodes in Aqueous Chloride Media

In situ scanning tunneling microscopy (STM) of the dissolution of a Cu(100) electrode in aqueous chloride media (HCl) was used to find the mechanism of reaction at the atomic level. Imaging the surface at potentials where no dissolution occurred resulted in a clear (root 2xroot 2)R45 deg Cl structure with an observed Cl-Cl distance of 0.35plus/minus0.02 nm, in agreement with previous ultrahigh vacuum surface analytical low-energy electron diffraction and Auger electron analysis studies of Cu(100) surfaces dosed with chlorine or energy electron diffraction and Auger electron analysis studies of Cu(100) surfaces dosed with chlorine or aqueous Cl exp - . Images acquired at potentials where dissolution was modest showed the preferred reaction sites were step edges with edges always retreating along the Cu(100) {100} direction. At still higher potentials, the rate increased and the reaction sites were still mainly the step edges.