Electrochemical Impedance Characterization of Nafion-Coated Carbon Film Resistor Electrodes for Electroanalysis

Carbon film disk electrodes with Nafion coatings have been characterized by electrochemical impedance spectroscopy (EIS) with a view to a better understanding of their advantages and limitations in electroanalysis, particularly in anodic stripping voltammetry of metal ions. After initial examination by cyclic voltammetry, spectra were recorded over the full potential range in acetate buffer solution at the bare electrodes, electrodes electrochemically pretreated in acid solution, and Nafion-coated pretreated electrodes in the presence and absence of dissolved oxygen. EIS equivalent circuit analysis clearly demonstrated the changes between these electrode assemblies. In order to simulate anodic stripping voltammetry conditions, spectra were also obtained in the presence of cadmium and lead ions in solution at Nafion-coated electrodes, both after metal ion deposition and following re-oxidation. Permanent changes to the structure of the Nafion film occurred, which has implications for use of these electrode assemblies in anodic stripping voltammetry at relatively high trace metal ion concentrations.