Kinetics of Aqueous Polysulfide Solutions: II . Electrochemical Measurement of the Rates of Coupled Electrochemical and Chemical Reactions by the Potential Step Method

Abstract

The kinetics of the aqueous polysulfide redox couple were investigated using a potential step technique in a solution 1M in S0 and 1.3M in total S2−, at pH 12. The low overpotential region (−20 to +20 mV) on cobalt and platinum electrodes was investigated from 25° to 80°C. The active species concentration was found to be several orders of magnitude lower than those of any of the major (poly)sulfide ions, and its temperature dependence corresponded to an Enormala of about 10 kcal/ mol. These results are consistent, with the active species being S2− . Deviations were found at temperatures above 45°C between experimental data and the simple analytical form for the current response for an electrode reaction with one rate‐determining step. The results agree with a new model that considers two rate‐determining steps, one of which is the reaction S42−⇆2S2− . The rate constants for this reaction determined using this new model agree with those measured for similar reactions.

Correlating Microstructure and Activity for Polysulfide Reduction and Oxidation at WS2Electrocatalysts

“…Electrochemical characterization.-All of the electrodes tested, including the carbon substrate, and the Pt counter electrode reached the same potential, −0.754 V with respect to an SCE, within a few minutes of immersion within the cell. This is consistent with reports in the literature, 10,29,77,78 and suggests that this potential is the reversible Nernst potential for polysulfide reduction and oxidation. Moreover, we assume, unless otherwise specified that all voltammetric and potentiostatic dc currents are faradaic in nature, and are selective toward polysulfide reduction and oxidation.…”

Mediator-free total cholesterol estimation using a bi-enzyme functionalized nanostructured gold electrode

“…With the incorporation of cysteamine, the sulphur ions at the surface of the Au nanostructures further facilitate the electrochemical oxidation-reduction of Au, resulting in an enhanced electrochemical current. 22 Also, the higher surface area provided by the smaller Au nanostructures results in faster electron transfer kinetics leading to an increase in the redox current.…”

Numerical modelling of a bromide–polysulphide redox flow battery

“…A number of mechanisms have been proposed for the bromide-polysulphide system under a range of conditions [25][26][27][28][29][30][31] including tribromide and polysulphide complexes, supersulphide radicals and intermediary steps. In this study a simple reaction mechanism is assumed:…”