Formation of Thick Layers of Iodine During the Anodic Oxidation of Iodide on a RDE: II . Open‐Circuit Behavior

Bejerano, T.; Gileadi, E.

doi:10.1149/1.2133143

Cited by 26 publications

(21 citation statements)

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“…The formation of I 2 -film layers during the electro-oxidation of I – has been reported in several previous studies. − To quantitatively analyze the amount of the I 2 -film, the mass change of the graphite/quartz composite electrode during a CV test was monitored using eQCM (Figure a). The resonance resistance showed a constant value with a random fluctuation, suggesting its little effect on the resonance frequency (Figure S1).…”

Section: Results and Discussionmentioning

confidence: 79%

“…The second decrease is ascribed to the formation of the I 2 -film on the electrode surface, preventing the charge-transfer reaction and/or mass transfer of I – ions from the bulk solution to the electrode surface. Most previous studies focused only on the reduction of the mass-transfer rate of I – ions. − They attributed the sudden drop of the current to an increase in the specific resistance of the I 2 -film because the film impedes the diffusion of I – ions. Here, we investigate the change in the charge-transfer resistance ( R ct ) at the electrolyte/electrode interface during the development of the I 2 -film.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Gokhshtein suggested that the I 2 -film experiences a phase transition from the initial liquid droplet to the thermodynamically stable crystalline phase, resulting in two distinct layers: a dense layer formed near the electrode surface that plays a major role for the current reduction and another porous layer that covers the dense phase and shows little influence on the anodic current. On the other hand, Bejerano and Gileadi focused on a different possible transition from an amorphous to crystalline phase on the basis of their open-circuit measurements. , They reported that during this transient, the specific resistance of the I 2 -film suddenly increased by 30 times, causing a sharp drop in the anodic current. Several researchers, including Gileadi et al, have adopted an ionic conductivity model that assumes that I – ions can effectively travel through the I 2 -film by a Grotthuss mechanism. − Most groups have ascribed the current reduction to the change in the specific resistance within the I 2 -film.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, Bejerano and Gileadi focused on a different possible transition from an amorphous to crystalline phase on the basis of their open-circuit measurements. , They reported that during this transient, the specific resistance of the I 2 -film suddenly increased by 30 times, causing a sharp drop in the anodic current. Several researchers, including Gileadi et al, have adopted an ionic conductivity model that assumes that I – ions can effectively travel through the I 2 -film by a Grotthuss mechanism. − Most groups have ascribed the current reduction to the change in the specific resistance within the I 2 -film. However, it is difficult to clearly define the specific resistance because the correlation between the film thickness and the current is not obvious even after the phase transition.…”

Section: Introductionmentioning

confidence: 99%

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Effect of an Iodine Film on Charge-Transfer Resistance during the Electro-Oxidation of Iodide in Redox Flow Batteries

Jang

Seong

Kim

et al. 2021

ACS Appl. Mater. Interfaces

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The use of iodide as the positive redox-active species in redox flow batteries has been highly anticipated owing to its attractive features of high solubility, excellent reversibility, and low cost. However, the electro-oxidation reaction of iodide (I − ) is very complicated, giving various possible products such as iodine (I 2 ), polyiodides (I 2n+1 − ), and polyiodines (I 2n+2 ) with n ≥ 1. In particular, the electro-oxidation of I − /I 3 − and I 3 − /I 2 occurs in competition depending on the applied potential. Although the former reaction is adopted as the main reaction in most redox flow batteries because I 3 − is highly soluble in an aqueous electrolyte, the latter reaction inevitably occurs together and a thick I 2 -film forms on the electrode, impeding the electro-oxidation of I − . In this study, we investigate the variation of the interface between the electrode and the electrolyte during the development of an I 2 -film and the corresponding change in the charge-transfer resistance (R ct ). Initially, the I 2 -film builds upon the electrode surface in the form of a porous layer and the aqueous I − ions can easily reach the electrode surface through pores inside the film. I − ions are electro-oxidized to I 3 − or I 2 at the interface between the aqueous I − phase and electrode with a small R ct of less than 16.5 ohm•cm 2 . Over time, the I 2 -film is converted into a dense layer and I − ions diffuse through the film in the form of I 3 − , possibly by a Grotthuss-type hopping mechanism. I 3 − can then be electro-oxidized to I 2 at the new interface between the I 2 -film and electrode, resulting in a dramatic 9-fold increase of R ct to 147.4 ohm•cm 2 . This increase of R ct by the dense I 2 -film is also observed in the actual flow battery. At high current densities above 400 mA•cm −2 , the overpotential begins to show an abrupt increase in the amplitude of more than 300 mV after reaching a critical charging capacity at which the dense I 2 -film appears to have begun to form on the felt electrode. Therefore, the I 2 -film exerts a serious negative effect on the performance of the flow battery depending on the current density and electrolyte SoC (state-of-charge).

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Section: Results and Discussionmentioning

confidence: 79%

Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of an Iodine Film on Charge-Transfer Resistance during the Electro-Oxidation of Iodide in Redox Flow Batteries

Jang

Seong

Kim

et al. 2021

ACS Appl. Mater. Interfaces

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“…It has been reported that aqueous iodide undergoes spontaneous oxidation upon chemisorption to form a layer of zerovalent atomic iodine on platinum electrodes at potentials between 0 and +0.4 V vs SCE 30,31. Under higher potentials, molecular iodine would be formed due to further deposition of atomic iodine, which can either lead to the formation of solid iodine 32,33 or dissolution into the solution phase. At higher concentrations of iodide (greater than ca.…”

Section: Resultsmentioning

confidence: 99%

Electrocatalytic Activation of Silver Nanowires‐modified Pt Electrode by Cyclic Voltammetry in Comparison with Differential Pulse Voltammetry in Halide Determination

Qin

Miao

et al. 2015

Electroanalysis

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Cyclic voltammetric (CV) and differential pulse voltammetric (DPV) measurements were carried out to assess the changes in electrode reactivity in halide determination with a silver nanowire‐modified platinum electrode. With DPV, successive voltammograms of the halide solution revealed progressive deterioration of the oxidation currents corresponding to Br− and Cl−, while those of I− increased largely. Comparatively, CV is stable and effective to remove precipitates due to the reduction process, in which, the concentrated effect alleviated and the amount of AgI decreased. CV was consequently suggested to be favorable for halide determination, while playing a role in electrocatalytic activation of the electrode.

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Direct Writing Unclonable Watermarks with an Electrochemical Jet

Speidel

Bisterov

Clare

2022

Adv Funct Materials

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Counterfeit parts result in significant losses per annum and are often dangerous, therefore they represent a serious concern for manufacturers and end users alike. Easily written but unclonable watermarks undermine the proposition of the counterfeiter. Here, a rapid electrochemical jet engraving routine is presented to encode robust materials with self-organized dendritic structures at length scales that can be imaged with a smartphone. Surface defects act as stochastically distributed seeds from which discrete pitting events can be propagated by translating the electrochemical field. While the vascular pathways can be directly written at the macro scale, the formation and propagation of microscale dendritic arms is chaotic, caused by the implicit randomness of the defect seeds and the supply of ions to the surface. The latter is confounded by random perturbations in the flow condition. Each engraved dendrite is unique, stable at high temperature (>500 °C) and can be subjected to rapid image recognition to allow individual mark identification at any point during part production and delivery, or through part lifetime.

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Formation of Thick Layers of Iodine During the Anodic Oxidation of Iodide on a RDE: II . Open‐Circuit Behavior

Cited by 26 publications

References 0 publications

Effect of an Iodine Film on Charge-Transfer Resistance during the Electro-Oxidation of Iodide in Redox Flow Batteries

Effect of an Iodine Film on Charge-Transfer Resistance during the Electro-Oxidation of Iodide in Redox Flow Batteries

Electrocatalytic Activation of Silver Nanowires‐modified Pt Electrode by Cyclic Voltammetry in Comparison with Differential Pulse Voltammetry in Halide Determination

Direct Writing Unclonable Watermarks with an Electrochemical Jet

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