Stochastic electrochemical analysis of electrochemically generated ethylpyridinium polybromide droplets: Evidence of Br/Br3/Br2 electro-oxidation in quaternary ammonium polybromide

Seulgi Shin, Dayoung Jung, Junghyun Chae, Jinho Chang

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Abstract

The stochastic event of Br electrolysis in electrochemically generated ethylpyridinium polybromide (EPyBr2n + 1) on Pt ultramicroelectrode (UME) was studied. The individual current spikes of the chronoamperograms (CAs) and the estimated charges associated with electro-reductive peaks from the cyclic voltammograms (CV) revealed that Br in EPyBr2n + 1 was electro-oxidized to Br3 and further to Br2. The experimentally estimated values regarding such electrochemistry of Br in EPyBr2n + 1 are as follows: 1) the stability constant of Br3 formation from Br and Br2 in EPyBr2n + 1 was estimated to 22.5 M− 1 based on the two voltammetric curves related to Br electro-oxidation in EPyBr2n + 1; 2) the maximum concentration of Br which can be electrolyzed in EPyBr2n + 1 was estimated to ca. 15.5 (± 4.9) M by fitting the bulk electrolysis model; 3) additionally, the minimum concentration of EPyBr(aq) in acidic solution required to generate the detectable individual current spikes in CAs was estimated as ca. 32 mM. It is noteworthy that the electrochemical behavior of Br in EPyBr2n + 1 turned out different from that in MEPBr2n + 1, which was reported previously, in that further oxidation of Br3 to Br2 was observed only in EPyBr2n + 1 but not in MEPBr2n + 1. This implies that the stability of Br3 is strongly dependent on quaternary ammonium cations, MEP+ and EPy+. A possible explanation for such stability difference in organic media (i.e. MEPBr2n+ 1 and EPyBr2n + 1) was also provided.

Original languageEnglish
Pages (from-to)123-130
Number of pages8
JournalJournal of Electroanalytical Chemistry
Volume802
DOIs
StatePublished - 2017 Oct 1

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Electrooxidation
Ammonium Compounds
Electrolysis
Electrochemistry
Cations
Positive ions
Oxidation
ethylpyridinium

Keywords

  • Bromine complexation agent
  • Electro-oxidation of Br-
  • Ethylpyridinium polybromide
  • Stochastic event analysis
  • Zn/Br redox flow battery

Cite this

@article{c1daaa9cf2be4658a892da0fc7cd96c9,
title = "Stochastic electrochemical analysis of electrochemically generated ethylpyridinium polybromide droplets: Evidence of Br−/Br3−/Br2 electro-oxidation in quaternary ammonium polybromide",
abstract = "The stochastic event of Br− electrolysis in electrochemically generated ethylpyridinium polybromide (EPyBr2n + 1) on Pt ultramicroelectrode (UME) was studied. The individual current spikes of the chronoamperograms (CAs) and the estimated charges associated with electro-reductive peaks from the cyclic voltammograms (CV) revealed that Br− in EPyBr2n + 1 was electro-oxidized to Br3− and further to Br2. The experimentally estimated values regarding such electrochemistry of Br− in EPyBr2n + 1 are as follows: 1) the stability constant of Br3− formation from Br− and Br2 in EPyBr2n + 1 was estimated to 22.5 M− 1 based on the two voltammetric curves related to Br− electro-oxidation in EPyBr2n + 1; 2) the maximum concentration of Br− which can be electrolyzed in EPyBr2n + 1 was estimated to ca. 15.5 (± 4.9) M by fitting the bulk electrolysis model; 3) additionally, the minimum concentration of EPyBr(aq) in acidic solution required to generate the detectable individual current spikes in CAs was estimated as ca. 32 mM. It is noteworthy that the electrochemical behavior of Br− in EPyBr2n + 1 turned out different from that in MEPBr2n + 1, which was reported previously, in that further oxidation of Br3− to Br2 was observed only in EPyBr2n + 1 but not in MEPBr2n + 1. This implies that the stability of Br3− is strongly dependent on quaternary ammonium cations, MEP+ and EPy+. A possible explanation for such stability difference in organic media (i.e. MEPBr2n+ 1 and EPyBr2n + 1) was also provided.",
keywords = "Bromine complexation agent, Electro-oxidation of Br-, Ethylpyridinium polybromide, Stochastic event analysis, Zn/Br redox flow battery",
author = "Seulgi Shin and Dayoung Jung and Junghyun Chae and Jinho Chang",
year = "2017",
month = "10",
day = "1",
doi = "10.1016/j.jelechem.2017.08.021",
language = "English",
volume = "802",
pages = "123--130",
journal = "Journal of Electroanalytical Chemistry",
issn = "1572-6657",

}

TY - JOUR

T1 - Stochastic electrochemical analysis of electrochemically generated ethylpyridinium polybromide droplets

T2 - Evidence of Br−/Br3−/Br2 electro-oxidation in quaternary ammonium polybromide

AU - Shin, Seulgi

AU - Jung, Dayoung

AU - Chae, Junghyun

AU - Chang, Jinho

PY - 2017/10/1

Y1 - 2017/10/1

N2 - The stochastic event of Br− electrolysis in electrochemically generated ethylpyridinium polybromide (EPyBr2n + 1) on Pt ultramicroelectrode (UME) was studied. The individual current spikes of the chronoamperograms (CAs) and the estimated charges associated with electro-reductive peaks from the cyclic voltammograms (CV) revealed that Br− in EPyBr2n + 1 was electro-oxidized to Br3− and further to Br2. The experimentally estimated values regarding such electrochemistry of Br− in EPyBr2n + 1 are as follows: 1) the stability constant of Br3− formation from Br− and Br2 in EPyBr2n + 1 was estimated to 22.5 M− 1 based on the two voltammetric curves related to Br− electro-oxidation in EPyBr2n + 1; 2) the maximum concentration of Br− which can be electrolyzed in EPyBr2n + 1 was estimated to ca. 15.5 (± 4.9) M by fitting the bulk electrolysis model; 3) additionally, the minimum concentration of EPyBr(aq) in acidic solution required to generate the detectable individual current spikes in CAs was estimated as ca. 32 mM. It is noteworthy that the electrochemical behavior of Br− in EPyBr2n + 1 turned out different from that in MEPBr2n + 1, which was reported previously, in that further oxidation of Br3− to Br2 was observed only in EPyBr2n + 1 but not in MEPBr2n + 1. This implies that the stability of Br3− is strongly dependent on quaternary ammonium cations, MEP+ and EPy+. A possible explanation for such stability difference in organic media (i.e. MEPBr2n+ 1 and EPyBr2n + 1) was also provided.

AB - The stochastic event of Br− electrolysis in electrochemically generated ethylpyridinium polybromide (EPyBr2n + 1) on Pt ultramicroelectrode (UME) was studied. The individual current spikes of the chronoamperograms (CAs) and the estimated charges associated with electro-reductive peaks from the cyclic voltammograms (CV) revealed that Br− in EPyBr2n + 1 was electro-oxidized to Br3− and further to Br2. The experimentally estimated values regarding such electrochemistry of Br− in EPyBr2n + 1 are as follows: 1) the stability constant of Br3− formation from Br− and Br2 in EPyBr2n + 1 was estimated to 22.5 M− 1 based on the two voltammetric curves related to Br− electro-oxidation in EPyBr2n + 1; 2) the maximum concentration of Br− which can be electrolyzed in EPyBr2n + 1 was estimated to ca. 15.5 (± 4.9) M by fitting the bulk electrolysis model; 3) additionally, the minimum concentration of EPyBr(aq) in acidic solution required to generate the detectable individual current spikes in CAs was estimated as ca. 32 mM. It is noteworthy that the electrochemical behavior of Br− in EPyBr2n + 1 turned out different from that in MEPBr2n + 1, which was reported previously, in that further oxidation of Br3− to Br2 was observed only in EPyBr2n + 1 but not in MEPBr2n + 1. This implies that the stability of Br3− is strongly dependent on quaternary ammonium cations, MEP+ and EPy+. A possible explanation for such stability difference in organic media (i.e. MEPBr2n+ 1 and EPyBr2n + 1) was also provided.

KW - Bromine complexation agent

KW - Electro-oxidation of Br-

KW - Ethylpyridinium polybromide

KW - Stochastic event analysis

KW - Zn/Br redox flow battery

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U2 - 10.1016/j.jelechem.2017.08.021

DO - 10.1016/j.jelechem.2017.08.021

M3 - Article

AN - SCOPUS:85029144621

VL - 802

SP - 123

EP - 130

JO - Journal of Electroanalytical Chemistry

JF - Journal of Electroanalytical Chemistry

SN - 1572-6657

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