The Low-Temperature Activity of Water in Concentrated KOH Solutions

Bro, P.; Kang, H. Y.

doi:10.1149/1.2408345

Cited by 15 publications

(14 citation statements)

References 2 publications

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“…If however one considers that the following reactions also contribute to Under certain conditions (i.e. [O,] high), the observed approximate linear relation between log t 1 1 2 and mKoH can be explained in terms of [I 71 since it is known (23, 24) that a,,,, a,,,, and [O,] all have an approximate exponential dependence o n m,,,, in the concentration range used even a t the low temperatures of this investigation (25).…”

Section: Formation and Decay Of 0-anodic Formationmentioning

confidence: 82%

Anodic Charging of Electrodes at Low Temperatures Studied by Electron Spin Resonance

Gardner¹,

Casey²

1974

Can. J. Chem.

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A study of anodic oxidation processes at several electrodes at low temperatures in KOH solutions is presented. The techniques of electron spin resonance have been used to identify intermediates. From a detailed kinetic analysis of the information obtained, the role of the formation and decay of 0 , -and certain metallic oxide radicals in the anodic charging of metal (hydr)oxide electrodes has been deduced.The formation of 03-and/or 02-, or neither, during anodic oxygen evolution seems to be controlled by the tightness of binding of OH to the surface (hydr)oxide which changes with the metal in the (inferred) order of increasing binding strength Cd, Pb, Ni. Pt.Once formed in solution, 0:,-decays slowly below 0 "C, slower the higher the KOH concentration. Primary dissociation, influenced by ion pair formation and by hydrolysis, controls the rate.Le produit O c se dtgage de plusieurs metaux dans 1'Blectrolyte KOH., durant I'oxidation anodique B basses temperatures. On peut mesurer la quantitt d' O; par la r.p.e., et ensuite faire une analyse cinttique des rtactions lorsqu'il se dttruit. Le comportement varie selon les metaux utilists durant les expiriences. L'ion CuOn2-se produit du cuivre, et 1'0.-ou 1'0:,-se produit du cadmium selon les conditions exptrimentales. L'O; est le seul produit qui peut Ctre ditectt par la r.p.e. de I'argent.En frais de rtsultats, on propose que I'inergie &adsorption de I'OH determine les produits, soit I'oxide bien chargi soil les radicaux libres dans I'electrolyte. I1 nous semble que l'ordre de lier I'OH serait Cd < Ag < Pb < Ni < Pt, une fonction de la structure des (hydr)oxides h la surface. Pour emmagasiner plus de charge anodique sur les electrodes il faut supprimer la formation de ]'On-et 1'01.L'03-se dttruit lentement B basses temperatures (<0 "C). La vitesse baisse si la concentration de KOH est plus forte. Un modtle thtorique est propose pour dtcrire les resultats. Can. J. Chem., 52,930(1974) IntroductionThe present work was directed towards a better Problems such as the slow rate of charge understanding of the processes which can and d o ceptance encountered in the electrical recharging Occur during some anodic oxidations (positiveof aqueous battery systems at low temperatures plate charging reactions) at low temperature. are due to a number ofcauses. ~i~~t , a decrease in Fortunately, certain free-radical intermediates temperature causes relative changes in the re-which are produced during the anodic oxidation versible electrode potentials of the reactions pas-at low temperatures in aqueous JSOH electrolyte sible. Secondly, increased polarizations and decay rather slowly and can be detected and their higher potentials at the anode and cathode occur, concentration followed by e.s.r. techniques. Thus because of kinetic and compositional barriers, in an earlier note (4) we indicated identification of increase in electrolyte viscosity, etc. AS a result, 0 3 -as a radical produced anodically on silver alternate side reactions, such as oxygen evolution and gave some of its properti...

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Section: Formation and Decay Of 0-anodic Formationmentioning

confidence: 82%

Anodic Charging of Electrodes at Low Temperatures Studied by Electron Spin Resonance

Gardner¹,

Casey²

1974

Can. J. Chem.

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“…Total solute mole fraction a n is the number of data points, and p is the number of parameters used in the osmotic virial equation. Adjusted R 2 of the fit and the maximum mole fraction of the data 19,24 are also given. (Predictions for a pore with a radius of 1 μm directly underlie predictions for the unconfined electrolyte.)…”

Section: Predictions Of the Role Of Compositionmentioning

confidence: 99%

“…Best fit of the mole-fraction-based osmotic virial equation to experimental data from references and for the freezing of unconfined aqueous KOH solutions. Eq and the properties in Table were used to convert the freezing point data from references and into osmole fraction as a function of mole fraction. The data was then fit to eq yielding k KOH * and B KOH * .…”

Section: Osmotic Virial Coefficients For Electrolytes Of Interestmentioning

confidence: 99%

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Freezing of Aqueous Electrolytes in Zinc–Air Batteries: Effect of Composition and Nanoscale Confinement

Liu

Chung

Elliott

2018

ACS Appl. Energy Mater.

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Zinc−air batteries, which typically employ aqueous electrolytes, have attracted much attention owing to their high energy density, low cost, and environmental friendliness. While the zinc−air battery is a promising solution for energy grid applications, freezing of the electrolyte is an important problem for operation in cold climates. The freezing point of the electrolyte can be affected not only by chemical composition but also by micro/nanoscale confinement in porous electrodes or separators, and this is the focus of our work. First, we find osmotic virial coefficients by fitting experimental freezing point data for various electrolytes that are used in zinc−air batteries. Second, we show how additives that improve the performance of the batteries may also lower the freezing point of the electrolyte system. Third, we show how the nanoscale confinement inside zinc−air batteries further decreases the freezing point; a 10 nm diameter capillary pore can suppress the local freezing point of the electrolyte by ∼10 °C. Finally, we map out the equilibrium mol% ice as a function of temperature, concentration, and confinement. This study provides insight that can be used to design specialized electrolytes for low temperature applications.

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“…A-hrp is the quantity of negative electrode precharge in ampere hour, di is the density of the initial KOH, and 0.34 is the conversion factor relating A-hr to equivalent weight of the negative electrode. The electrolyte concentration can be estimated for any condition of charge or discharge from the following equation [8] where A-hrNc is the nominal capacity of the cell, 1.2 is the factor that accounts for the capacity in excess of the nominal cell capacity, 0.104 is the equivalent weight of KOH removed from electrolyte during charge, and 0.670 is the equivalent weight of water produced during charge. CHG is the fractional charge related to the cell capacity by CHG-----1.00-DOD, where DOD is the fractional depth of discharge.…”

Section: Concentration and Depth O] Discharge (Dod)--asmentioning

confidence: 99%

Changes in Alkaline Electrolyte Concentration and Its Effect on the Open‐Circuit Potentials in the Nickel‐Cadmium Cell

Halpert

May

1977

J. Electrochem. Soc.

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In the electrode reactions of the nickel cadmium cell there is an inter= change of H~O and OH-at the electrodes, depending on whether the cell has been charged or discharged. The calculations described below are based on a reaction involving KOH adsorption/desorption. The results from experimental cells are found to be consistent with t'his model. Electrolyte concentrations are calculated for different states of charge of a cell where ~he effect of precharge is considered. The open-circuit potentials (negative, positive, and cell) are calculated for various KOH concentrations (10.3-45.2%) and temperatures (0~176The calculated temperature coefficient for the cell potential is found to be --0.45 mV/deg, which is comparable to that found in previous experiments.The concentration and distribution of aqueous potassium hydroxide (KOH) electrolyte in a sealed nickel cadmium cell has been the subject of considerable discussion. The reactions at both electrodes during charge and discharge involve the production or utilization of hydroxyl ion (OH-) or water (H~O), which directly affects concentration. The potential developed between the cadmium hydroxide (negative) electrode and the nickel hydroxide (positive) electrode depends upon the concentration of the potassium hydroxide electrolyte. The open-circuit potentials for the cell and each half-cell varies with the concentrations of the hydroxide and temioerature. In addition to the changes at each electrode, there is a net change in concentration of t'he electrolyte in the cell as a whole. During charge there is an increase in water; during discharge, a decrease in water. If we consider a more correct reaction equation, there is also a decrease in OH-on charge associated with KOH adsorption at the positive electrode and increase during discharge. The net effect is a significant decrease in concentration from beginning to end of charge, and an increase during discharge. The extent of precharge must also be considered in that during this process OH-is converted to water that also dilutes the electrolyte. The Basic Cell ReactionThe sealed nickel-cadmium ceil consists of electrodes containing cadmium and nickel hydroxides as the active materials, and aqueous potassium hydroxide as the electrolyte. The open-circuit potential of the cell is determined in part by the concentration of the hydroxide, as can be seen by the equations for the half-cell potentials involving the cadmium and nickel * Electrochemical Society Active Member. ASEE/NASA Faculty Fellow. Key words: nickel-cadmium, alkaline electrolyte, open-circuit potentials and activities. hydroxide electrodes and the composite equation for the potential of the cell. The reaction at the positive electrode is 2NiOOH + 2H20 + 2e ~ 2Ni(OH)2 + 2 OH-[1] and for the negative electrode Cd (OH)2 + 2e r Cd -5 2 OH-[2]The over-all reaction for the cell is therefore the difference of the tv;o half-cell reactions discharge 2NiOOH -5 2H20 -5 Cdr 2Ni(OH)2 -5 Cd(OH)s charge [a]

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The Low-Temperature Activity of Water in Concentrated KOH Solutions

Cited by 15 publications

References 2 publications

Anodic Charging of Electrodes at Low Temperatures Studied by Electron Spin Resonance

Anodic Charging of Electrodes at Low Temperatures Studied by Electron Spin Resonance

Freezing of Aqueous Electrolytes in Zinc–Air Batteries: Effect of Composition and Nanoscale Confinement

Changes in Alkaline Electrolyte Concentration and Its Effect on the Open‐Circuit Potentials in the Nickel‐Cadmium Cell

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