The electrochemical interface between Au(1 1 1) and 1-butyl-3-methyl-imidazolium hexafluorophosphate has been studied by cyclic voltammetry and electrochemical impedance spectroscopy in a potential range, which might be considered to be the double-layer charging region for Au(1 1 1) is such an environment. The corresponding equivalent circuit is given by a capacity in parallel to a constant phase element (CPE). The high-frequency value of the capacity - that is. the double-layer capacitance - is about 6-7 mu F/cm(2) over the whole potential range under study, whereas the CPE peaks at a potential, which coincides with the potential of zero total charge (pztc), as determined by immersion experiments. This latter element expresses the kinetics of the re-structuring of the interfacial region. In situ STM measurements reveal marked structural differences positive and negative of the pztc. (C) 2010 Elsevier Ltd. All rights reserved.