A Quartz Crystal Microbalance Study of the Electrochemical Reaction at the Interfaces of Platinum/Aqueous Solution and Iron/Aqueous Solution

Abstract

The adsorption of the sulphate ions on the-platinum electrode in sulphuric acid solution and the breakdown of the passivity in the iron electrode in the chloride-containing and chloride-free alkaline solutions have been investigated by using in-situ electrochemical quartz crystal microbalance (EQCM) technique combined with cyclic voltammetry (CV), potentiodynamic polarization and potentiostatic current transient techniques. In the case of the platinum electrode, the combined electrogravimetric and voltammetric results are indicative of the onset of the adsorption of the sulphate ions at an applied potential between the two characteristic potentials of hydrogen desorption, above which the adsorption occurs: The adsorption of the sulphate ions was quantitatively analyzed with cyclic electrogravimetric data combined with those determined from radio tracer technique and Fourier transform infra-red (FTIR) spectroscopy by other researchers. In the case of the iron electrode, the electrogravimetric data obtained simultaneously with the potentiodynamic polarization data indicate the pitting and high-voltage breakdown of the oxide film in the chloride-containing and -free solutions, respectively, Preventing the crevice corrosion from occurring around the O-ring at the quartz crystal, the electrogravimetric curve showed that the pit initiation time measured by EQCM coincides with that time determined by current transient experiment.