Closure to “Discussion of ”The Stability and Solubility of AgO in Alkaline Solutions’ [T. P. Dirkse and B. Wiers (pp. 284–287, Vol. 106)]”

Dirkse, T. P.; Wiers, Brandon H.

doi:10.1149/1.2427233

Cited by 34 publications

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“…[1][2][3][4][5]. Recent studies have been stimulated in large measure by applications of the Ag/AgO electrode in batteries of high energy-tomass ratio (6)(7)(8)(9). In addition, however, the system has intrinsic interest, as evidenced by the numerous theories which have been advanced to explain various features of the oxidation and reduction kinetics.…”

Section: Introductionmentioning

confidence: 99%

Anodic behavior of silver in alkaline solutions

Dignam¹,

Barrett²,

Nagy³

1969

Can. J. Chem.

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Data, covering a range of pH and temperature, were obtained for the anodic oxidation of electropolished silver and the results compared with electrodes which had undergone repeated oxidation and reduction cycles. The behavior of the electrode is, in the main, complex, showing, for example, autopotential cycling under certain galvanostatic conditions (-3 pA/cmZ, 25 "C, 0.7 N NaOH), the period of oscillation being about t h. Several other hitherto unreported phenomena were also observed. The main conclusions reached are (i) that 2 different mechanisms are involved in the anodic formation of AgzO on silver electrodes in basic electrolytes resulting in 2 types of film, 1 mechanism involves a dissolution-precipitation process, the other possibly a direct interfacial reaction; (ii) that the reduction of anodically formed Ag,O films either electrochemically or in hydrogen at 800 OC leaves behind a highly porous,layer of silver metal; and (iii) that the limiting AgzO film thickness is probably determined by a diffusion process occurring within the film.

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Section: Introductionmentioning

confidence: 99%

Anodic behavior of silver in alkaline solutions

Dignam¹,

Barrett²,

Nagy³

1969

Can. J. Chem.

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“…This overshoot has been the subject of several investigations, and different causes have been assigned for its appearance (16,21). It can be seen in Fig.…”

Section: Resultsmentioning

confidence: 97%

“…The electrolyte acquired a dark brown color, and some sediment appeared at the bottom of the cell, indicating considerable solubility of the active compounds in the electrolyte. Taking the solubility of the silver oxides in 1M KOH as 2.10-4M Ag (22,23), the silver in the 200 ml of electrolyte amounts to only 4.3 rag. The residue formed in cycling which settled at the bottom of the cell was less than 50 rag.…”

Section: Resultsmentioning

confidence: 99%

A Coulogravimetric Study of the Sintered Silver Electrode in 1 Molar Potassium Hydroxide

Langer

Patton

1967

J. Electrochem. Soc.

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Weighing of a sintered silver electrode while immersed in electrolyte during cathodic and anodic reaction reveals breaks in the weight change-coulomb curves. The different slopes can be explained by the volume change during phase transformation, affecting the buoyancy of the electrode. These breaks coincide with the potential changes of the plate, measured against a reference electrode.The silver electrode in alkali electrolyte has gained considerable prominence in the construction of batteries offering high discharge rates and high energy densities per unit weight and volume. The outstanding properties of this electrode have long been recognized (1-4), but a complete understanding of its behavior is still lacking (5,.6). Moreover, since efficient electrodes are usually of the porous type, an exhaustive interpretation of their behavior requires an understanding of the many factors affecting this type of electrode. Among these are the expansion and contraction of the active mass.This volume change affecting the buoyancy is studied by weighing continuously the porous silver electrode in 1.0M potassium hydroxide as electrolyte during the complete cathodic and anodic cycle. Simultaneously, the corresponding number of coulombs involved is determined, and the potential of the electrode is recorded against a suitable reference electrode and correlated with the change in weight. A similar procedure was used by Schoop (7) at the turn of the century, but it has not been practiced frequently since (8, 9). TheoryIf a silver plate suspended in the electrolyte is oxidized a~aodically to silver oxide, the change in the weight of the immersed electrode is the algebraic sum of several related effects, principally (i) a weight increase due to the added mass of reacted oxygen, and (ii) an altered buoyancy lift due to the volume change of the electrode by the newly formed compound. There is still another factor affecting the buoyancy of the sample considered to be minor. The density of the electrolyte around the electrode is changing, due to the consumption of ions at the interface and the heat that is generated by the passage of the current.In the following discussion we assume that minor effects can be neglected, provided low current densities are used, so that concentration differences in the electrolyte are small since equalized by diffusion. Additionally, for these conditions, the density gradients are not large enough to produce convection of the electrolyte which may still further influence the weight of the sample. The reaction must be carried out at potentials where no gas evolution will occur since small bubbles formed in or adhering to the electrode will alter its true weight. We also assume that the reaction products are only sparingly soluble in the electrolyte.Under these conditions we can derive an equation for the weight change of the electrode in the electrolyte. Let a mass of silver mAg and density dAg be immersed in a liquid electrolyte of density ds. The weight of the silver in the solution mAg s will be mAgs_-~n...

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“…This suggests that Eq. This reference electrode can give a rather significant junction potential with alkaline solutions (13) and they made no correction for junction potentials. Apparently the Zn(OH)2(H20)2 and Zn(OH)3(H20)-species do not govern the EMF behavior.…”

Section: Resultsmentioning

confidence: 99%

The Behavior of the Zinc Electrode in Alkaline Solutions: III . The Equilibrium Potential

Dirkse

1979

J. Electrochem. Soc.

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The EMF of the zinc electrode in a variety of alkaline solutions has been measured at 25~ The total ionic strength of these solutions was carefully controlled. Departures from Nernstian behavior appear to be due to junction potentials involving the OH-ions. The concentration of the electrolyte in the reference electrode is a major contributor to this non-Nernstian behavior. The solute species governing the EMF of the zinc electrode in these solutions is the Zn(OH)4 ~-ion.* Electrochemical Society Active Member. vestigate the effect of ionic strength on the zinc electrode process in the Tafel region.

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Closure to “Discussion of ”The Stability and Solubility of AgO in Alkaline Solutions’ [T. P. Dirkse and B. Wiers (pp. 284–287, Vol. 106)]”

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Cited by 34 publications

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Anodic behavior of silver in alkaline solutions

Anodic behavior of silver in alkaline solutions

A Coulogravimetric Study of the Sintered Silver Electrode in 1 Molar Potassium Hydroxide

The Behavior of the Zinc Electrode in Alkaline Solutions: III . The Equilibrium Potential

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