Anodic Behavior of Hafnium in Anhydrous Electrodissolution-Coupled Hafnium Alkoxide Synthesis

Round 1

Reviewer 1 Report

Review Report

Manuscript ID: processes-2202570

Title: Anodic behavior of hafnium in anhydrous electrodissolution-coupled hafnium alkoxide synthesis

In this study, the detailed electrochemical investigation of the Hf corrosion/dissolution in the Et4NCl or Et4NHSO4 based anhydrous system was successively done.

I strongly recommend that the Editorial Office consider this manuscript for publication after minor revision.

Reviewer’s Suggestion

Line 87. It should be 4 electrons as reaction products.

Lines 115-116. When describing CV measurements authors have to indicate the initial potential also. Which method for IR drop compensation did the authors use?

Figure 2. This figure is totally unnecessary. It’s a general figure of electrochemical assembly.  

Lines 207-208. Express the Tafel slope results with significant figures. (suggestion 3 decimal places)

Line 212. Express the corrosion rate results with significant figures. (suggestion 2 decimal places)

Above suggestions also stand for Table 1.

 

General observation: All figures are relatively pale; if authors have time I would suggest using more intense colors. 

Author Response

Response to Reviewer 1 Comments

Comments to the Author:

In this study, the detailed electrochemical investigation of the Hf corrosion/dissolution in the Et₄NCl or Et₄NHSO₄ based anhydrous system was successively done. I strongly recommend that the Editorial Office consider this manuscript for publication after minor revision.

We appreciate the reviewer for the kind comments and respond to reviewer’s comments/suggestions on a point-to-point basis below.

Reviewer’s Suggestion

Point 1: Line 87. It should be 4 electrons as reaction products.

Response 1: Thank the reviewer for pointing this out. We have corrected the R1 in the revised manuscript.

 

Point 2: Lines 115-116. When describing CV measurements authors have to indicate the initial potential also. Which method for IR drop compensation did the authors use?

Response 2: We appreciate the reviewer's constructive comments and have added the full range of CV scanning potentials (-1 V - 3 V, 4 V, and 5 V for Et₄NCl; -0.65 V - 3 V, 4 V, and 5 V for Et₄NHSO₄). This manuscript adopted the current interrupt (CI) method for IR drop compensation.

 

Point 3: Figure 2. This figure is totally unnecessary. It’s a general figure of electrochemical assembly.

Response 3: Thanks to the reviewer for pointing this out. The Figure 2 is a general diagram of an electrochemical assembly, which is helpful to enable readers clearly understand the practical electrochemical measurement/operation of the anodic behaviour and reproduce the original experiment.

 

Point 4: Lines 207-208. Express the Tafel slope results with significant figures. (suggestion 3 decimal places)

Response 4: We thank the reviewer's constructive comments. Each Tafel slope was expressed with significant figures.

 

Point 5: Line 212. Express the corrosion rate results with significant figures. (suggestion 2 decimal places) Above suggestions also stand for Table 1.

Response 5: We thank the reviewer's constructive comments. Each corrosion rate was expressed with significant figures.

 

Point 6: General observation: All figures are relatively pale; if authors have time I would suggest using more intense colors.

Response 6: Thanks for pointing this out. We have tried to add some intense colors into the figures.

Reviewer 2 Report

The paper is well-organized and clearly written. I just have a couple of minor questions:

1.       In Fig. 3, where is the 4V CV curve? Is it completely overlapping with that of the 3V?

 

2.       Several types of data such as CV, Tafel, etc, and based on which different quantifications were provided. All results have suggested that Hf corrosion/dissolution is a few times greater in Et4NCL than that in the Et4NHSO4. The author suggested that Et4NCL facilitates the Hf pitting kinetics. Moreover, due to the accumulation/adsorption of HSO4^- on the surface of the passive film, the dissolution of the Hf passive layer was hindered. Can the author elaborate a bit why this is the case?

Author Response

Response to Reviewer 2 Comments

Comments to the Author:

The paper is well-organized and clearly written. I just have a couple of minor questions:

We appreciate the reviewer for the kind comments and respond to reviewer’s comments/suggestions on a point-to-point basis below.

 

Point 1: In Fig. 3, where is the 4V CV curve? Is it completely overlapping with that of the 3V?

Response 1: Thanks for pointing this out. We have extracted the CV curve of 3V into the inset of Figure 3, to clearly exhibit the CV curves at different scan ranges.

 

Point 2: Several types of data such as CV, Tafel, etc, and based on which different quantifications were provided. All results have suggested that Hf corrosion/dissolution is a few times greater in Et₄NCl than that in the Et₄NHSO₄. The author suggested that Et₄NCl facilitates the Hf pitting kinetics. Moreover, due to the accumulation/adsorption of HSO₄^- on the surface of the passive film, the dissolution of the Hf passive layer was hindered. Can the author elaborate a bit why this is the case?

Response 2: We acknowledge the reviewer for the comments. The Et₄NCl system reflects an efficient pitting mechanism of the anodic Hf dissolution, indicating a gradual puncture on passive film and initiation and propagation of corrosion on bare Hf. The Et₄NHSO₄ system exhibits a weak corrosion mechanism under the passive film, with dissolution/corrosion of the hafnium sample occurring within the passive film and diffusion into the bulk solution through the small pores. This is because HSO₄^- ions are not sufficient to corrode through the passive film on the electrode surface, resulting in a high kinetic hindrance to the dissolution/corrosion of Hf under the spontaneously formed porous passive film and the diffusion of dissolved Hf⁴⁺ cations and large ionophores (HSO₄^-) through the pores of the passive film. Comparing the above two systems, we conclude that the Hf dissolution/corrosion is thermodynamically and kinetically easier to induce in the Et₄NCl system than in the Et₄NHSO₄ system.

Reviewer 3 Report

 

Report:

The authors report on the anodic Hf corrosion/dissolution mechanism and kinetics in Et₄NCl and Et₄NHSO₄-based anhydrous electrolytes. The manuscript is well-written, and the content good explained and presented. I recommend this for publication after the following improvements have been made.

1.      Page 3: The cyclic voltammetry section only gives the upper voltage limit. Please state the complete measurement window.

 

2.      Page 4: Butler-Volmer equation (E1): In the exponent for the anode reaction, the transfer coefficient a₀ is used, and for the cathodic part b₀. However, b is only used for single electron transfer reactions and a for multistep electron transfer reactions. So please write for the anodic part a_a and the cathodic part a_c. Also, make the same changes for E2, too.

 

3.      Figure 3: There is no graph for 3V. Please check and add the data.

  

4.      At the End of each section, the authors should compare and discuss their data concerning the existing literature.

 

 

Author Response

Response to Reviewer 3 Comments

Comments to the Author:

The authors report on the anodic Hf corrosion/dissolution mechanism and kinetics in Et₄NCl and Et₄NHSO₄-based anhydrous electrolytes. The manuscript is well-written, and the content good explained and presented. I recommend this for publication after the following improvements have been made.

We appreciate the reviewer for the kind comments and respond to reviewer’s comments/suggestions on a point-to-point basis below.

 

Point 1: Page 3: The cyclic voltammetry section only gives the upper voltage limit. Please state the complete measurement window.

Response 1: We appreciate the reviewer's constructive comments and have supplemented the full range of CV scanning potentials (-1 V - 3 V, 4 V, and 5 V for Et₄NCl; -0.65 V - 3 V, 4 V, and 5 V for Et₄NHSO₄) in the revised manuscript.

 

Point 2: Page 4: Butler-Volmer equation (E1): In the exponent for the anode reaction, the transfer coefficient a0 is used, and for the cathodic part b0. However, b is only used for single electron transfer reactions and a for multistep electron transfer reactions. So please write for the anodic part aa and the cathodic part ac. Also, make the same changes for E2, too.

Response 2:Thanks to the reviewer for pointing this out. We have revised E1 and E2 in the revised manuscript.

 

Point 3: Figure 3: There is no graph for 3V. Please check and add the data.

Response 3: Thanks to the reviewer for pointing this out. We have extracted the CV curve of 3V into the inset of Figure 3, to clearly exhibit the CV curves at different scan ranges.

 

Point 4: At the End of each section, the authors should compare and discuss their data concerning the existing literature.

Response 4: Thanks for pointing this out. Little existing literatures are available as a comparison option, as the optional eligible comparative system is little, much less the comparable results obtained by the similar analysed method.