Assessment of Ion Size Effects in the Diffuse Double Layer with Use of an Integral Equation Approach

Fawcett, W. Ronald; Smagala, Thomas G.

doi:10.1021/jp0475234

Cited by 14 publications

(26 citation statements)

References 14 publications

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“…The analysis of the values of the diffuse layer potential calculated according to the Monte Carlo method as well as generalized mean spherical approximation [41][42][43] would give more information.…”

Section: Discussionmentioning

confidence: 99%

Electroreduction of Hexaamminecobalt(III) Cation on Bi(hkl) Electrodes from Weakly Acidified LiClO[sub 4] Solutions

Härk

Lust

2006

J. Electrochem. Soc.

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The cyclic voltammetry and rotating disk electrode methods have been used for investigation of electroreduction kinetics of the hexaamminecobalt͑III͒ cations on the electrochemically polished Bi planes. The rate constant for the heterogeneous electroreduction reaction of the ͓Co͑NH 3 ͒ 6 ͔ 3+ cation on the Bi͑001͒ and Bi͑011͒ planes in x M LiClO 4 + 0.001 M HClO 4 aqueous base electrolyte solutions has been established and the results have been compared with the data for the Ag͑110͒, Au͑hkl͒, and Hg electrodes as well as with the data for Bi͑hkl͒ in x M HClO 4 solutions. In the region of zero charge potential, the value of the experimental transfer coefficient ␣ exp is slightly higher than 0.5 and depends on the crystallographic structure of the Bi plane. For more concentrated base electrolyte solutions, the values of apparent transfer coefficient ␣ app , corrected for the double-layer effect, are practically independent of the base electrolyte concentration and slightly depend on the electrode polarization. Noticeably different values of the double-layer-corrected rate constant k het 0 and ␣ app for the Bi͑001͒, Bi͑011͒, Bi͑111͒, Hg, and Ag͑110͒ electrodes from the data for Au͑hkl͒ planes have been explained by the different water and ClO 4 − adsorption energies at the metals under discussion.The electroreduction of ͓Co͑NH 3 ͒ 6 ͔ 3+ complex cation is observed as a model reaction for theoretical analysis of so-called outersphere reaction. 1-12 However, the rate constant, corrected for the electrical double-layer effect, depends noticeably on the chemical nature of the electrode. 4,5,10,11 It was found that the rate constant of ͓Co͑NH 3 ͒ 6 ͔ 3+ reduction at Au single-crystal planes at fixed electrode potential increases in the order Au͑100͒ Ͻ Au͑111͒ Ͻ Au͑110͒ Ͻ Au͑210͒, i.e., with increasing the reticular density of the surface studied. 7 After correction for the electrical double-layer effect, the kinetic data fall on one common plot for all Au electrodes studied, and a single value of the apparent transfer coefficient ͑␣ app ͒ is obtained for this electrode reaction. The electric double-layercorrected rate constant depends on some specific properties of the electrode and the redox species, such as the zero charge potential or the electronic work function of the single-crystal plane and its relation to the standard potential. [3][4][5]7,[9][10][11] The reduction kinetics of hexa-aqua-iron ͑III͒ ion was studied at Au͑hkl͒ ͑at various concentrations of HClO 4 as the base electrolyte 8 ͒ but differently from ͓Co͑NH 3 ͒ 6 ͔ 3+ reduction; 7 the electron transfer coefficient depends on the crystallographic structure of the electrode surface. It was found that ␣ app increases with reticular density of the Au͑hkl͒ planes. 8 Our preliminary studies of ͓Co͑NH 3 ͒ 6 ͔ 3+ electroreduction at Bi͑hkl͒ ͑Ref. 11͒ show that ␣ app obtained depends on the crystallographic structure and increases slightly with the reticular density of the plane. Differently from the Au͑hkl͉͓͒Co͑NH 3 ͒ 6 ͔ 3+ + HClO 4 + H 2 O system, 7 the heterog...

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Section: Discussionmentioning

confidence: 99%

Electroreduction of Hexaamminecobalt(III) Cation on Bi(hkl) Electrodes from Weakly Acidified LiClO[sub 4] Solutions

Härk

Lust

2006

J. Electrochem. Soc.

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“…The details of the Monte Carlo simulations are discussed in our previous work [25]. The MC calculations were performed for three different ionic sizes, five different concentrations, and eight different positive charge densities.…”

Section: Comparisons With Monte Carlo Simulationsmentioning

confidence: 99%

“…Henderson and Blum [20,21] showed that these same integral equations could be solved in a non-iterative manner if the ion-wall correlation functions were assumed to be those given by GC theory. This method, hereinafter referred to as the HB approach, has been extended in several recent papers [22][23][24][25][26]. However, Henderson and Blum [20] clearly state that the limitation of their method is that it computes only the potential drop across the diffuse layer, but not the ion-wall correlation functions or potential profiles.…”

Section: Introductionmentioning

confidence: 99%

A novel differential equation approach to modeling ion size effects in the diffuse double layer

Smagala

Fawcett

2006

Journal of Electroanalytical Chemistry

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“…Later work by Fawcett and Smagala showed that the HB estimates of Ξ 0 and H 0 are not sufficiently good especially for higher values of the field E . They obtained improved expressions for Ξ 0 and H 0 by forcing the value of φ d to agree with MC estimates of this quantity.…”

Section: Integral Equation Approach and The Msa Parametersmentioning

confidence: 98%

New Developments in the Theory of the Diffuse Double Layer

Fawcett

Smagala

2006

Langmuir

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The role of ion size effects in determining diffuse layer properties is considered. Monte Carlo data relevant to this question are reviewed. Then the integral equation approach to the problem is considered with an emphasis on attempts to derive an analytical equation for the potential drop across the diffuse layer. An empirical model for ion size effects is described that allows one to estimate not only the diffuse layer potential drop but also the diffuse layer capacity, the ionic surface excesses, and the potential distribution in the diffuse layer. It is demonstrated that the resulting model can easily be applied by experimentalists to the analysis of experimental data for double layer phenomena in electrochemistry and colloid science.

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Assessment of Ion Size Effects in the Diffuse Double Layer with Use of an Integral Equation Approach

Cited by 14 publications

References 14 publications

Electroreduction of Hexaamminecobalt(III) Cation on Bi(hkl) Electrodes from Weakly Acidified LiClO[sub 4] Solutions

Electroreduction of Hexaamminecobalt(III) Cation on Bi(hkl) Electrodes from Weakly Acidified LiClO[sub 4] Solutions

A novel differential equation approach to modeling ion size effects in the diffuse double layer

New Developments in the Theory of the Diffuse Double Layer

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