ELECTROCHEMICAL REDUCTION OF THIONYL CHLORIDE STUDIED BY CYCLIC VOLTAMMETRY, CHRONOCOULOMETRY, AND CHRONOAMPEROMETRY

Electrochemical reduction of thionyl chloride has been studied at a molybdenum electrode employing cyclic voltammetric, chronocoulometric, and chronoamperometric techniques. The charge transfer process is affected strongly by the film formed on the electrode surface during the reduction. The exchange rate constants, k0, of the order of 10(6) cm/s were observed at fresh electrodes, whereas much smaller constants of about 10(-10) cm/s were observed at film-covered electrodes. The activation energy at the film-covered electrode for the electron-transfer reaction was dependent on whether the measurements were made with the cell temperature increased or decreased. Chronocoulometric results indicate that the film formation takes place at the electrode surface during the electrochemical reduction of thionyl chloride. The thickness of this film estimated to be about 10(-5) cm from chronocoulometric and chronoamperometric experiments. Different diffusion behaviors were observed in three different time zones in chronoamperometric experiments.