Chronopotentiometry based on diffusion of mobile nonelectroactive species

Braunstein, J.; Bronstein, H. R.; Truitt, J.

doi:10.1016/s0022-0728(73)80479-6

Cited by 6 publications

(14 citation statements)

References 5 publications

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“…Because the diffusion-limited currents for A1 anodization, ilim (A1), and for C1-oxidation at Pt, ilim(C1-) are controlled by diffusion of C1-to the electrode surface, the D value used in Eq. [4] for both processes is the same. Therefore, the ratio of the diffusion-limited currents for the two processes, ilim(A1)/i~im(C1 ), yields the ratio of their n values.…”

Section: Normal Pulse Voltammetric Analysis Of At Anodization--mentioning

confidence: 91%

“…From the data obtained it is not possible to confirm the process leading to the first wave. The diffusion-controlled limiting current, in~, for normal pulse voltammetry is given by inm = nFAC(D/~tp) v2 [4] where n is the number of electrons involved in the process, F is the Faraday constant, C is the concentration of the diffusing species, D is the diffusion coefficient of the diffusing species, and tp is the pulse width (17). For the anodization of A1, both n and D are unknowns.…”

Section: Normal Pulse Voltammetric Analysis Of At Anodization--mentioning

confidence: 99%

“…[4] (17), C1-diffusion coefficients, Dch were calculated. Plots of ihm VS. tp -1~2 are linear for both A1 anodization, Fig.…”

Section: Normal Pulse Voltammetric Analysis Of At Anodization--mentioning

confidence: 99%

“…If the increase in current is assumed to result from the increase in Dch then taking the natural log of Eq. [4] and rearranging gives In (ilim) = 1/2 In (Doe-Ea/RT) + In [nFAC/(~t) u2] [10] or in (ilim) = -Ea/2RT + K [11] where Do and K are constants and Ea is the activation energy for diffusion (25). A plot of In (ilia) vs. lIT gives a straight line over the temperature range 26 ~ to 80~ as seen in Fig.…”

Section: Chronoamperometric Study Of Al Anodization--becausementioning

confidence: 99%

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Aluminum Anodization in a Basic Ambient Temperature Molten Salt

Carlin

Osteryoung

1989

J. Electrochem. Soc.

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Aluminum anodization has been studied in the basic A1C13:1-methyl-3-ethylimidazolium chloride (ImC1) ambient temperature molten salt (A1C13:ImC1 molar ratio <1.0). The anodization process was studied as a function of chloride anion concentration. Two different anodization processes are observed with onset potentials of approximately -1.1 and 0 V. The more cathodic anodization involves formation of the tetrachloroaluminate anion and exhibits a limiting current controlled by diffusion of chloride to the electrode surface. The number of chlorides required for each A1 anodized was determined to be 4.6 _+ 0.4. The more anodic anodization shows no diffusion control. A value for the diffusion coefficient of chloride was obtained which is lower than previously reported; the difference involves using an n value of 1, rather than 2/3. No reduction of the tetrachloroaluminate anion was observed even at elevated temperatures.Numerous studies have been carried out on the redox chemistry of aluminum in A1C13:MC1 molten salts, where MC1 is an alkali metal chloride (1-6) or M + is an organic cation, e.g., N-butylpyridinium chloride (BuPyC1) or 1-methyl-3-ethylimidazolium chloride (ImC1) (7,8). In these chloroalumlnate melts the major equilibrium determining the anion species is 2AIC14 ~ A12C1c + C1[1]for which the equilibrium constant is 1.06 x 10 -7 for A1C13:NaC1 at 175~ (9) and 8 • 10 -'s for A1C13:ImC1 at 40~ (10). In melts with an A1C13:MC1 ratio >1.0, an acidic melt, the dominant anion species are tetrachloroaluminate and heptachlorodialuminate ions. In melts with an A1C13:MC1 ratio <1.0, a basic melt, the anion species present are tetrachloroaluminate and chloride. The electrochemistry of an aluminum electrode in these chloroaluminate melts is strongly dependent upon the melt composition.In the high temperature A1C13:alkali metal chloride melts, most studies have been performed in the acidic composition region. Aluminum deposition in acidic melts involves a nucleation process and exhibits a limiting current controlled by diffusion of the heptachlorodialuminate anion to the electrode surface (1). A number of interesting features of A1 anodization in these acidic alkali metal melts have been observed. During anodization of an A1 wire into acidic A1C13-KC1-NaC1 melts at 105~176 a passivation of the A1 anode was observed with a resultant sudden decrease in the anodic current which then achieves a steadystate value (2). This passivation was attributed to the formation of an insoluble, poorly conducting layer of A1C13 on the electrode surface. The quantity of anodic current passed before passivation occurred could be increased by cathodic prepolarization which created a diffusion layer close to the electrode depleted in A1C13, thus allowing more A1 to be anodized into the melt before formation of this passive layer of A1C13. As expected, passivation due to salt precipitation also occurred during A1 deposition. However, a decrease in the cathodic current was followed by a rapid increase in the current due to dendrite formation (...

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Section: Normal Pulse Voltammetric Analysis Of At Anodization--mentioning

confidence: 91%

Section: Normal Pulse Voltammetric Analysis Of At Anodization--mentioning

confidence: 99%

“…[4] (17), C1-diffusion coefficients, Dch were calculated. Plots of ihm VS. tp -1~2 are linear for both A1 anodization, Fig.…”

Section: Normal Pulse Voltammetric Analysis Of At Anodization--mentioning

confidence: 99%

Section: Chronoamperometric Study Of Al Anodization--becausementioning

confidence: 99%

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Aluminum Anodization in a Basic Ambient Temperature Molten Salt

Carlin

Osteryoung

1989

J. Electrochem. Soc.

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“…Although the subject of ionic migration in electrolytic mass transport has previously been discussed by many authors (2)(3)(4)(5)(6)(7)(8)(9)(10)(11), most of these treatments have been confined to steady-state limiting current cases. In chronopotentiometry, one is interested in determining the functional relationship between the applied current density, the transition time and the surface concentration of the species involved in the electrochemical reaction.…”

mentioning

confidence: 99%

Migration Considerations in Chronopotentiometric Analysis

Mak

Cheh

1988

J. Electrochem. Soc.

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A theoretical analysis has been conducted to evaluate the effect of migration in galvanostatic processes and to provide a fundamental basis for assessing the limits of applicability of Sand's equation in chronopotentiometric measurements. The results of the computation show that the diffusion potential is a significant driving force for migration transport within the diffusion layer. The square root of the transition time is inversely proportional to the applied current density, irrespective of the degree of migrational interaction in the system. Three case studies are presented to illustrate the effect of migration in different electrochemical processes. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.174.255.3 Downloaded on 2015-03-13 to IP Vol. 135,No. 9

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Molten Salts Data: Diffusion Coefficients in Single and Multi-Component Salt Systems

Janz¹,

Bansal²

1982

Journal of Physical and Chemical Reference Data

122

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The property of diffusion is one of the basic properties of fluid systems. In molten salts, more than 700 studies have been reported to August, 1980, with more than 15 diffusion measurement techniques. A critical examination of these studies with a review of the techniques is presented. The results for more than 140 salt systems are reported in this communication as a series of data tables, with numerical values, value judgements, and literature citations. Silicates, slags, and oxide melts are excluded.

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Chronopotentiometry based on diffusion of mobile nonelectroactive species

Cited by 6 publications

References 5 publications

Aluminum Anodization in a Basic Ambient Temperature Molten Salt

Aluminum Anodization in a Basic Ambient Temperature Molten Salt

Migration Considerations in Chronopotentiometric Analysis

Molten Salts Data: Diffusion Coefficients in Single and Multi-Component Salt Systems

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