Catalytic generation of chlorine with slight overpotential by micellar ferrocene

Ferrocene solubilized with poly(vinylpyrrolidone) in aqueous KCl solution exhibited a well-defined voltammetric peak at 1.33 V vs. Ag∣AgCl at a platinum electrode. The wave was attributed to the oxidation of chloride to chlorine, demonstrated by smell of chlorine, by a view of formation of gas bubbles, by coloration through the reaction with diethyl-p-phenylene diamine, and by the increase in the anodic current with the concentration of chloride. Since no wave was observed in the ferrocene-free solution or KCl-free solution in this potential domain, the reaction mechanism was suggested to be the oxidation of chloride into chlorine catalyzed by micellar ferrocene. The potential at the foot of the wave (1.08 V) was less positive that the standard potential of Cl2/Cl−, and hence the reaction may be useful for enhancing the energetic efficiency at chlor-alkali industry. The value of the peak current was one-sixth the theoretical diffusion-controlled current, and was proportional to the square-root of the potential scan rate.