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Article
Peer-Review Record

The Difference in the Effects of IR-Drop from the Negative Capacitance of Fast Cyclic Voltammograms

Electrochem 2023, 4(4), 460-472; https://doi.org/10.3390/electrochem4040030
by Yuanyuan Liu 1, Koichi Jeremiah Aoki 2 and Jingyuan Chen 1,2,*
Reviewer 1:
Reviewer 2: Anonymous
Reviewer 3:
Electrochem 2023, 4(4), 460-472; https://doi.org/10.3390/electrochem4040030
Submission received: 13 August 2023 / Revised: 13 September 2023 / Accepted: 22 September 2023 / Published: 23 October 2023

Round 1

Reviewer 1 Report

This paper discusses the deformation of peaks on cyclic voltammetry during high scan rate and contributes the factor to solution IR drop. The point is novel and the mathematical proof is sound. The reviewer hereby has a few questions that hope the author could help address:

1. Since IR drop is considered the main contributor to the peak deformation here, how does the distance of electrodes affect the deformation of peaks during a CV scan?

2. It is commonly believed that the higher the scan rate, the thicker the diffusion layer is. How does this affect the IR drop? How does the author consider if this has any contribution to the change of solution IR drop?

3. If the solution is under agitation, does the conclusion of this paper still hold true?

Author Response

Thank you very much for reviewing our manuscript, ID electrochem-2583307, on the I-R drop. The opinions were generally positive for the publication if we respond to the criticisms sufficiently and revise the manuscript. We respond here to each criticism and will suggest our revision. Red letters are by the reviewer.

 

This paper discusses the deformation of peaks on cyclic voltammetry during high scan rate and contributes the factor to solution IR drop. The point is novel and the mathematical proof is sound. The reviewer hereby has a few questions that hope the author could help address:

 

We agree on all the criticism, and revise the manuscript at the three points.

 

  1. Since IR drop is considered the main contributor to the peak deformation here, how does the distance of electrodes affect the deformation of peaks during a CV scan?

This criticism is on a source of solution resistances. Solution resistance is composed of molar conductivity of ions (or diffusion coefficients), ionic concentrations, the charge number of ions, and geometry of electrochemical cells. Since they have been well-documented in a textbook of physical chemistry, they are not a subject of this article. The reviewer paid attention to a distance between electrodes as a source of the IR-drop. However, the solution resistance used for voltammetry is often not proportional to the distance in real cells, because it is determined with the Laplace equation for voltage within a cell. For example, parallel electrodes have hardly been used for voltammetry, and the IR-drop at microelectrodes is almost independent of the electrode distance. Therefore, it is unreasonable to address a general rule for the geometry and CV-shape. A response to the criticism is to add to the 48-line

"It is ascribed not only to ionic conductivity but also geometry of cells and electrodes as a solution of the Laplace equation for the voltage."

 

  1. It is commonly believed that the higher the scan rate, the thicker the diffusion layer is. How does this affect the IR drop? How does the author consider if this has any contribution to the change of solution IR drop?

This question is about the relation of the IR-drop with scan rates. It has been already summarized in Table 1 in connection with heterogeneous kinetics. However, it may be kind to address the conventionally observed fact of the higher currents at higher scan rates. We would like to rewrite at the 45 line

"the increase in scan rates" as

"the increase in scan rates which enhance the currents".

 

  1. If the solution is under agitation, does the conclusion of this paper still hold true?

This question is on the effects of convection of solution, which are important to extend electrochemical concepts in a wide domain. Our conclusion may not be valid for convection. We rewrote at the 262 line

"a diffusion-controlled voltammograms" as.

"a diffusion-controlled voltammograms in quiescent solution" .

 

Sincerely

Reviewer 2 Report

This paper seems to be written in a very sophisticated way. I really appreciate if authors can convince me about the importance of their results. It has nothing to do with science or quality of paper but in my opinion to the fact that in the present form this work is addressed to the very limited number of reader. Authors please do something to make your work claer for broader audience and make clear importance of the procedure applied. 

Author Response

Thank you very much for reviewing our manuscript, ID electrochem-2583307, on the I-R drop. The opinions were generally positive for the publication if we respond to the criticisms sufficiently and revise the manuscript. We respond here to each criticism and will suggest our revision. Red letters are by the reviewer.

This paper seems to be written in a very sophisticated way. I really appreciate if authors can convince me about the importance of their results. It has nothing to do with science or quality of paper but in my opinion to the fact that in the present form this work is addressed to the very limited number of readers. Authors please do something to make your work clear for broader audience and make clear importance of the procedure applied. 

 

All experimental results at fast scan voltammograms are deviated from ideal behavior. Most of electrochemists have been satisficed with the deviation. However, we tried to challenge the deviation, and hence the description becomes "sophisticated". We know that there are a few readers for this manuscript. A limited number of readers is characteristic of theoretical papers, and we have experienced this fact during a half century. However, a life-time of citation of a paper is long.

The reviewer recommends us to make the importance of this work clear. In order to explain the importance to broader readers, we would like to add to the 56-line

"These problems result from enhancement of currents due to an increase in scan rates, and are often encountered at conventional, electrochemical measurements".

We agree on "sophisticated expression" at 125-127 lines, which we would like to delete,

We do not necessarily agree with the criticism, because a work "uncompensated resistance" has been addressed at a cost of one section of two pages in the monograph by A.J. Bard and has been used totally 47 times in the whole monograph.

Sincerely

Reviewer 3 Report

Dear Editor,

 

The manuscript with the ID electrochem-2583307 deals with the effects of IR-drop on voltammetric peak potentials and currents.

The authors write that a negative capacitance is established through a mechanism described in lines 154-158. However, this mechanism is not very clear: firstly, the FcTMA species (used as an electrochemical probe) is a cation whose counter-ion is never mentioned (it is found as Cl-, I-, BF4- on the market). In the proposed mechanism, FcTMA is oxidized so that a doubly positively charged species should be formed. It is not at all clear how this species manages to form a dipole with the Cl- ions present in the solution (coming from the support electrolyte KCl), taking into account all the other ions present in the solution. The authors should explain the proposed mechanism more clearly, in particular how the formation of a dipole between ions at the electrode interface is justifiable.

Other remarks:

line 86: why is the KCl concentration not specified?

line 190: reference is made to a "supporting information" file, which however only contains an uncommented graph

 In conclusion, the work is unclear in several parts; in my opinion, it is suitable for publication after major revision

Author Response

Please see attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Although the paper was not very much improved I accept authors explanation given in the rebutal letter and recommend this paper for publication

Reviewer 3 Report

Dear Editor,

the paper may be accepted for publication in the current revision

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