REDOX REACTIONS OF HYDROSULFIDE IONS ON THE PLATINUM-ELECTRODE .2. AN IMPEDANCE SPECTROSCOPY STUDY AND IDENTIFICATION OF THE POLYSULFIDE 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 40 mu F cm(-2) at open circuit potential. When electrolysis commenced the double layer capacitance was greatly reduced (<5 mu F 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.