The reduction and oxidation of vanadium in acidic aqueous sulfate solutions at mercury electrodes

Israel, Yecheskel; Meites, Louis

doi:10.1016/0022-0728(64)87003-0

Cited by 22 publications

(12 citation statements)

References 27 publications

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“…The rather large minimum exchange current obtained for the V(III)/V(II) couple in the adsorbed state contrasts with the smaller exchange currents previously measured for this couple in electrolytes where no reactant adsorption was involved (7)(8)(9)(10)(11)(12)(13)(14). This large difference might be regarded as an instance of true catalysis by the electrode surface, i.e., electrocatalysis.…”

Section: A Similar Dependence On the Concentration Of V(iii)contrasting

confidence: 71%

The Adsorption of Vanadium(III) on Mercury from Thiocyanate Solutions and Its Electrochemical Consequences

Anson¹,

Čaja²

1970

J. Electrochem. Soc.

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The adsorption of V (III) on mercury electrodes in thioeyanate electrolytes has been measured chronocoulometrically. The adsorption is not strongly dependent on potential except in the vicinity of the V (III)/V (II) half-wave potential. The adsorbing species is a V(III)-thiocyanate complex containing one or more thiocyanates. The adsorption of V(II) also occurs, but is much weaker than that of V(III). A minimum value for the exchange current for the V(III)/V(II) couple in the adsorbed state has been estimated coulostatically. Although this exchange current is quite large, 0.5 A/cm 2, its magnitude can be largely accounted for by the enhancement of the reactants' surface concentrations produced by their adsorption.The spontaneous adsorption of electrochemical reactants on the surface of electrodes often produces complications in the study of the kinetics of their electrode reactions. An electrode process that can proceed by more than one pathway, e,g., via both the adsorbed and unadsorbed reactants, corresponds to a complex equivalent circuit which contains elements that cannot be evaluated in separate experiments in the absence of the reactants. As a result, a larger number of kinetic parameters must be extracted from the rate data, and confidence in the accuracy and uniqueness of the resulting kinetic parameters is weakened. Under these circumstances, it is advantageous to have independent quantitative information on the extent of adsorption of the reactants because the kinetic data can then be analyzed with one less adjustable parameter.The technique of chronocoulometry (1) is well suited to provide the desired quantitative adsorption data. It has been applied in the present study to evaluate the adsorption of V(III) and V(II) on mercury electrodes in thiocyanate solutions. The V(III)/V(II) system was chosen for several reasons. It offered an opportunity to compare the adsorption of a transition metal redox couple with the extensively studied anioninduced adsorption of white metal cations (2-6) [Cd(II), Zn(II), Pb(II), In(III)]. Second, the equilibrium adsorption of V(III) and V(II) could be measured in poised solutions containing both halves of the redox couple, thus allowing the potential dependence of the adsorption in the vicinity of the half-wave potential to be determined. Analogous data for the white metal cations are less straightforward to obtain because of the difficulties associated with the preparation and storage of metal amalgam electrodes. Finally, the V(III)/V(II) system was attractive because the electrode kinetics of the couple have been extensively studied (7-14) in electrolytes where no reactant adsorption occurs. It was hoped that a comparison of these rates with those measured with adsorbed reactants would contribute to an understanding of the effect of adsorption on the rate of electrochemical charge transfer for a simple redox reaction. ExperimentalTechniques.--The adsorptions of V(III) and V(II) (which shows very little adsorption) were evaluated at potentials removed from the half-wave...

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Section: A Similar Dependence On the Concentration Of V(iii)contrasting

confidence: 71%

The Adsorption of Vanadium(III) on Mercury from Thiocyanate Solutions and Its Electrochemical Consequences

Anson¹,

Čaja²

1970

J. Electrochem. Soc.

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“…The vanadium redox‐flow battery (VRFB) is the most studied redox‐flow battery system to date, although the suitability of acid‐soluble di‐ to pentavalent vanadium was first discovered in 1986 143. Before this, basic electrochemical research had been done on vanadium, mostly at platinum and mercury electrodes 144–146. The formation of a film on the platinum electrodes, slow VO 2 + /VO 2+ reactions, irreversible V 3+ /V 2+ reactions at carbon felt electrodes, and high costs resulted in further research in the frame of the NASA redox‐flow batteries project being ruled out 9.…”

Section: Battery Chemistrymentioning

confidence: 99%

The Chemistry of Redox‐Flow Batteries

et al. 2015

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The development of various redox-flow batteries for the storage of fluctuating renewable energy has intensified in recent years because of their peculiar ability to be scaled separately in terms of energy and power, and therefore potentially to reduce the costs of energy storage. This has resulted in a considerable increase in the number of publications on redox-flow batteries. This was a motivation to present a comprehensive and critical overview of the features of this type of batteries, focusing mainly on the chemistry of electrolytes and introducing a thorough systematic classification to reveal their potential for future development.

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“…A VRB utilizes the V 2+ /V 3+ and V 4+ (VO 2+ )/V 5+ (

{VO}_{2}^{+}

) couples at 1 mol/L in 2–3 mol/L H 2 SO 4 and achieve high current density at reasonable potentials. In our system, the V 3+ /V 4+ (VO 2+ ) couple has its inherent disadvantage that it requires removing an oxygen atom from the vanadium atom in the reduction process, and this can be inefficient . Thermodynamically, use of V 2+ /V 3+ could also reduce Fe 3+ , but as discussed in Introduction, V 2+ is very unstable in acidic environment.…”

Section: Discussionmentioning

confidence: 99%

Engineering Acidithiobacillus ferrooxidans growth media for enhanced electrochemical processing

Mercado

Berlinger

et al. 2014

AIChE Journal

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The chemolithoautotroph Acidithiobacillus ferrooxidans has been proposed as a potential electrofuel synthetic platform, and its growth medium is engineered to increase its conductivity and energy density, thereby improving viability of the process. The ion V 31 is used as an indirect electron supplier together with Fe 21 to grow A. ferrooxidans to increase the energy density of the medium, overcoming the Fe 31 solubility limit. A medium containing 10 mM Fe 21 with 60 mM V 31 was able to support cell growth to a final cell concentration very similar to medium of 70 mM Fe 21 . Integration of the biological process with an electrochemical reactor requires, for economical operation, a medium with high ionic conductivity. This is achieved by the addition of salt, and Mg 21 was found to be least toxic to the bacterium. A concentration of 500 mM Mg 21 is optimal considering constraints on bacterial growth and electrochemistry.

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The reduction and oxidation of vanadium in acidic aqueous sulfate solutions at mercury electrodes

Cited by 22 publications

References 27 publications

The Adsorption of Vanadium(III) on Mercury from Thiocyanate Solutions and Its Electrochemical Consequences

The Adsorption of Vanadium(III) on Mercury from Thiocyanate Solutions and Its Electrochemical Consequences

The Chemistry of Redox‐Flow Batteries

Engineering Acidithiobacillus ferrooxidans growth media for enhanced electrochemical processing

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