Potentiodynamic electrochemical impedance spectroscopy. Copper underpotential deposition on gold

Copper underpotential deposition on polycrystalline gold was examined by potentiodynamic electrochemical impedance spectroscopy (PDEIS). The time evolution of the ac response was acquired as 3D plots of frequency response versus applied potential, and these data were later processed with an equivalent circuit analyser built into the virtual spectrometer. The dependences of the equivalent circuit parameters on potential revealed different responses of nitrate and sulphate. Nitrate adsorption pseudocapacitance, and the inverse of the adsorption pseudoresistance, both exhibited peaks in a narrow range of Cu monolayer growth, while sulphate affected a wider potential range and gave two desorption peaks in the anodic scan. Intrinsic irreversibility of the constituent processes was revealed by cyclic redox transformations of the Cu monolayer. (C) 2003 Elsevier Science B.V. All rights reserved.