Redox reactions of hydrosulphide ions on the platinum electrode—II. An impedance spectroscopy study and identification of the polysulphide intermediates

Impedance spectroscopy was used to confirm the presence of a poorly conductive sulphur layer on a platinum electrode during the electrolysis of HS −. The double layer capacitance was found to be close to 40μF cm −2 at open circuit potential. When electrolysis commenced the double layer capacitance was greatly reduced (< 5μF cm −2). The charge transfer resistance increased to few hundred ohms cm 2 during electrolysis. Double potential chronocoulometric experiments were also performed. The chronocoulometric analysis showed that the average stoichiometry of the intermediate polysulphide ions in the electrolysis reaction was S 2.5 2− in the anodic step and S 4.3 2− in the cathodic step.