New electrochemical and in situ surface X-ray diffraction results on Cu(111) in chloride containing acidic electrolytes (pH 1-3) are presented. Electrochemical characterization by cyclic voltammetry and current transients was carried out in different aqueous electrolytes as a function of the pH and the chloride concentration of the solution. The electrochemical data indicate coadsorption of chloride with an oxygenated species in an intermediate potential range, followed by a complete replacement of the oxygenated species by a close-packed chloride adlayer at the positive end of the double layer regime. The slow kinetics and the X-ray scattering results suggest that the adsorption of the oxygenated species is accompanied by structural changes of the Cu surface, most probably the formation of a surface oxide layer. (C) 2013 Elsevier B.V. All rights reserved.