Electrochemical immittance spectroscopy applied to the study of the single crystal gold/aqueous perchloric acid interface

The technique of electrochemical immittance spectroscopy has been used for characterisation of the interface at Sold single crystal electrodes in aqueous solutions of perchloric acid in the absence of Faradaic processes. The results obtained for low index crystallographic orientations, namely, (100), (110) and (111) are compared to those obtained earlier for the (210) orientation. The experimental results are analysed by fitting them to a simple equivalent circuit consisting of a resistor in series with a constant phase element representing respectively, the solution resistance, R-s, and the distributed impedance of the double layer, Z(CPE). The dependence of the parameters constituting the constant phase element, namely the pre-exponential factor, Y-0, and the fractional exponent, n(f), on the orientation of the electrode surface, on the electrode potential and on the solution concentration are discussed. The relationship of these parameters to the surface energy of the single crystals is discussed. (C) 1997 Elsevier Science S.A.