The influence of chloride on the initial anodic dissolution of Cu3Au(1 1 1)

We report a detailed in situ X-ray diffraction study of the influence of chloride on the atomic structure evolution at the solid-electrolyte interface during the selective dissolution of Cu from a Cu3Au(1 1 1) surface immersed in 0.1 M H2SO4. We disclose that the formation of the initial ultrathin Au-rich (1 1 1) with an inverted stacking sequence, as recently observed at Cu3Au(1 1 1) in contact with pure 0.1 M H2SO4, is strongly influenced by adding 5 mM HCl. The main finding is a negative shift of about 150 mV of the critical potential at which the ultra-thin Au-rich layer transforms into thicker Au islands. The presented results support the view that it is not a thermodynamic driving force, but rather the rate of surface diffusion that dominates the formation of the structures of the metallic layer.