Kinetics and Mechanism of Silver Chloride Electroformation during the Localized Electrodissolution of Silver in Solutions Containing Sodium Chloride

Abstract

The electroformation of normalAgCl during electro‐oxidation of Ag in neutral normalNaCl solutions is investigated by using potentiostatic and potentiodynamic techniques complemented with SEM observation and EDAX. The kinetics of the electroformation of normalAgCl is interpreted through a complex model that implies the formation of adsorbed normalAgCl species at the submonolayer level, the electrodissolution of Ag through the normalAgCl submonolayer diffusing out of the electrode as a complex ion, and the nucleation and growth of a tridimensional normalAgCl phase. This layer is formed initially as an island‐type deposit that includes normalAgCl precipitation from the solution adjacent to the electrode. The overall process is discussed in terms of a sum of nucleation and growth reactions under diffusion control (multiple region process). The electrode surface is considered as a sum of regions, each one involving its own characteristic growth rate. A probabilistic distribution of regions is postulated to calculate the current transients under a constant potential step. Fitting parameters can be reasonably interpreted at the molecular level. The proposed mechanism correlates with the complex chemical and electrochemical reactions expected for Ag in normalNaCl solutions.

A bespoke reagent free amperometric chloride sensor for drinking water

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