Bi(III) Ion Electroreduction in the Presence of Ethanol and Sodium 1‐Octanesulfonate at a Thin‐Layer Amalgam Electrode (Renewable Liquid Silver Amalgam Film Electrode); Kinetic and Thermodynamic Aspects

This study investigates the Bi(III) ions electroreduction in aqueous chlorate(VII) and aqueous-ethanolic chlorate(VII)-supporting electrolytes (SE) in the presence of the anionic surfactant sodium 1-octanesulfonate (1OSASS) over a range of temperatures. Electrochemical techniques, including direct current (DC) polarography, cyclic voltammetry (CV), and square-wave voltammetry (SWV), were used to evaluate both kinetic and thermodynamic parameters. Increasing ethanol concentration led to a decrease in the standard heterogeneous electron transfer rate constant (k_s), despite an increase in the diffusion coefficient of the oxidised species (D_ox). Rising temperature and surfactant concentration caused a shift in the formal potential (E_f ⁰) and an increase in redox peak separation (ΔE), indicating reduced process reversibility. Activation parameters, including activation energy (E_a), enthalpy (ΔH⁰), entropy (ΔS⁰), and Gibbs free energy (ΔG⁰), were determined using the Arrhenius and Eyring equations. The results confirm that 1OSASS exhibits a 'cap-pair' effect, likely due to competitive adsorption and complexation, significantly affecting redox kinetics. Overall, the study highlights the complex influence of the solvent-surfactant system on the structure of the electrical double layer (EDL) and on the kinetics and mechanism of the Bi(III) ions electroreduction process.