Silver/Silver Chloride Electrodes: Surface Morphology on Charging and Discharging

Abstract

Transport modes were determined from examinations of morphology for electrochemical oxidation and reduction within electrodes consisting of beds of silver spheres 37.2 μm in diameter in 1NnormalKCl and subjected to 5.0 mA cm−2 applied current density. Oxidation proceeded via silver dissolution, probably at dislocation sites, followed by diffusion and, then, deposition of normalAgCl in characteristic, bulbed mounds which grow together to form layers of approximately uniform thickness. normalAgCl film thickness, for the case of partially covered underlying silver, was about 3500Aå and distance from silver dissolution pits to normalAgCl deposition sites was found to be increased from 4,000 to 40.000Aå as the local transfer current density became larger within the sphere bed. Reduction of anodically formed normalAgCl on partially covered silver proceeded by an opposite path: solution and diffusion of normalAgCl , and deposition of silver on preferred sites of surrounding bare silver surface.

The physical and chemical characterization of electrochemically reformed silver surfaces

“…( O m~Ycnr ), it is propos ed t h a t the i n t er -n o d u l a r c l e f t s are q u i t e deep . In no cases were crv st a ll ites observable in the reformed layer [ 13 ] .…”

“…3C) inter-nodule clefts and boundaries [13] become more apparent , suggestive of the growth of nodules both on top of and 0 into one another. These clefts are on the order of 50 -100 A across , and they may be involved in the cap illary condensation model recentl y proposed [22) to account for the observed potential step Raman spectroelectrochetnistry [6] of p y r i d in e a t t h i s reformed su r f ac e .S mal1 pores of diame ters less than the resolution of the SEN ( <30 A) may also con tribute to this phenomenon .…”

“…It should be noted that for either process the dissolution site and deposi tion site are different and that there is evidence for preferential nucl eation sites [13].…”

“…The mechanism by which this reformation process occurs may be summarized by the following sequence of dissolution , comp lexat ion , transport and deposition after Katan , et al [13]:…”

A New Salt Bridge Based on the Hydrophobic Room-Temperature Molten Salt

“…[5][6][7] Usually, to suppress the dissolution of AgCl from the reference Ag/AgCl electrode into the concentrated KCl solution, the KCl solution used as the internal solution is saturated with AgCl, and hence contains complex ions, primarily AgCl 2 À and AgCl 3 2À . 8,9 Upon contact with a dilute aqueous solution at the junction, these species precipitate as AgCl and the junction may be clogged with these precipitates. Fourth, due to the kinetic nature of the diffusion potential formed at the liquid junction, the ljp depends on the details of the mass transport at the junction.…”