Electrochemical Synthesis of Palladium–Selenide Coatings

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this work, the authors prepared a series of coating materials by electrochemical deposition using different potentials and electrolytes. There are many problems found in the article, and the author has not indicated the practical application significance of this material, which needs further discussion. The paper cannot be accepted in its present version. A major revision is required.

1)    A document insertion formatting error occurs at line 132, and the author needs to check the document formatting carefully.

2)    Line 157.158 and many other font sizes are inconsistent. The author needs to check and modify the font size to be the same size

3)    What does -0.25÷-0.6V mean in line 163?

4)    The scale is mixed with the background, and the image number covers more spectral area in Figure 4.

5)    It is insufficient for the authors to use SEM and XRD to determine the structural characteristics of the materials. As we all know, SEM only shows the topography of a small area, and we are not sure what the other areas are like.

6)    The author only introduced how to prepare coating materials with different structure contents, but did not test their performance differences. I do not know what is the significance of these materials.

 

7)     Some state-of-the-art literature is missing, such as, ACS Catalysis 2020, 10 (19), 11371; Coatings 2023, 13(11), 1875; Carbon Neutralization 2022;1:4-5

Comments on the Quality of English Language

None

Author Response

The authors sincerely thank the referees for their hard work and insightful comments. The manuscript was corrected under the reviewers' comments. The following corrections were made:

R1:

In this work, the authors prepared a series of coating materials by electrochemical deposition using different potentials and electrolytes. There are many problems found in the article, and the author has not indicated the practical application significance of this material, which needs further discussion. The paper cannot be accepted in its present version. A major revision is required.

• A document insertion formatting error occurs at line 132, and the author needs to check the document formatting carefully.

The fonts in the document were corrected

• Line 157.158 and many other font sizes are inconsistent. The author needs to check and modify the font size to be the same size

The fonts in the document were corrected

• What does -0.25÷-0.6V mean in line 163?

The description of the voltammogram in line 163 was improved to make it more understandable.

• The scale is mixed with the background, and the image number covers more spectral area in Figure 4.

The letters describing individual photos have been made smaller. Unfortunately, at this point, we cannot sharpen the image enough to make the scale more visible. An additional description regarding scale has been added to the legend.

• It is insufficient for the authors to use SEM and XRD to determine the structural characteristics of the materials. As we all know, SEM only shows the topography of a small area, and we are not sure what the other areas are like.

We are aware of the limitations of the scanning electron microscopy technique. The areas we selected are relatively small compared to the entire electrode surface. During surface research, we tried to select the most representative areas possible, which would show how the surface topography changes depending on the parameters used. We included additional photos in the supplementary materials before the thermal treatment process. The photos were taken in other areas of the same electrodes, which confirms the repeatability of the surface topography of the tested coatings.

• 6)    The author only introduced how to prepare coating materials with different structure contents, but did not test their performance differences. I do not know what is the significance of these materials.

In the first research stage, our primary goal was to determine the possibility of synthesising Pd-Se coatings and how the electrolysis process parameters affect the coatings' basic properties. In the following research stage, we plan to investigate the properties of the synthesised coatings. Based on the literature, we know, among other things, that the obtained materials may have very good catalytic properties for some processes, such as water splitting or oxygen reduction. Another essential element is the stability of these materials and corrosion resistance in the environment in which they will work. It requires a large amount of research, the results of which would go beyond the current topic. The above research is currently being conducted in our laboratory and will be the subject of the subsequent publication.

• Some state-of-the-art literature is missing, such as, ACS Catalysis 2020, 10 (19), 11371; Coatings 2023, 13(11), 1875; Carbon Neutralization 2022;1:4-5

I appreciate the importance of the above publications. Still, it was very difficult to find a connection between the subject matter of the above articles and the main topic of our publication.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Overall, this article provided a detailed investigation into the electrochemical synthesis of palladium-selenium coatings, focusing on the factors that influence the deposition process, respectively, the influence of the concentration of individual reagents on the mechanism and kinetics of electrode reactions and the properties of the resulting coatings. The findings from this research could have applications in various fields, such as materials science, surface engineering or electrochemistry. 

The conclusions are supported by the results presented in detail. The references are mostly up-to-date, and appropriate to the study carried out.

Author Response

The authors sincerely thank the referee for familiarising with the manuscript and for the opinion.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript by Prof. Kowalik et al. describes the electrosynthesis of PdxSey thin films. The influence of the Pd and Se concentration on the formation of PdxSey thin films is investigated. There are a few suggestions that require the author’s attention.

(1) It is recommended to provide the XRD simulated data of Pd4Se, Pd7Se4 and Pd17Se15 for comparison in Fig. 3.

(2) The XRD signals in Fig. 3 are relatively weak. It is not easy to characterize the species of PdxSey. The author should explain in detail how the PdxSey is characterized.

(3) P11, Line 333-334,

The formation of the needles in Fig. 4b and 4f is due to the intense hydrogen evolution upon the reduction as stated by the author. It is in contrast to the CV results in which HER does not occur after -0.6 V.

(4) The annealing process under Ar seems to have a great impact on morphology of the think film of Fig. 4c (vs. Fig. S2c). Is there any explanation to the observation?

(5) What is the thickness of the PdxSey thin film?

(6) What is the resulting pH value after the electrodeposition?

(7) The image resolution in Fig. 1 and 3 is poor. Resolution improvement is required.

(8) P5, Line 164, The anodic peak A1 -> The anodic peak A4?

(9) P9, Line 263, Fig. 1a -> Fig. 3a?

 

The most important issue is, the author shall emphasize the method to control the formation of the Pd17Se15 thin film. The author shall elaborate this issue.

 

Comments on the Quality of English Language

it's fine.

Author Response

The authors sincerely thank the referees for their hard work and insightful comments. The manuscript was corrected under the reviewers' comments. The following corrections were made:

This manuscript by Prof. Kowalik et al. describes the electrosynthesis of PdxSey thin films. The influence of the Pd and Se concentration on the formation of PdxSey thin films is investigated. There are a few suggestions that require the author’s attention.

• It is recommended to provide the XRD simulated data of Pd4Se, Pd7Se4 and Pd17Se15 for comparison in Fig. 3.

Simulated data of Pd4Se, Pd7Se4 and Pd17Se15 have been added to the supplementary materials. Due to so many diffractograms, compiling all the data in one figure is not easy. Adding simulated data would make the graphs smaller and, therefore, even less readable. The resolution and brightness of the charts have been improved, and thus, the readability of the charts as well.

• (2) The XRD signals in Fig. 3 are relatively weak. It is not easy to characterize the species of PdxSey. The author should explain in detail how the PdxSey is characterized.

The intensity of the signal results from the thickness of the coating. The coatings are thin and do not exceed 4 μm. Moreover, the coatings have an amorphous structure after deposition, which makes their analysis difficult. Thermal treatment was intended to improve the degree of crystallisation of the coatings and thus highlight the reflections from the individual phases present in the coatings. We used a relatively low temperature to avoid evaporation of selenium. After processing, new reflections appeared, but not very intense. Phase identification included comparing the obtained reflections with standard safety data sheets for palladium-selenium compounds, pure palladium and pure selenium, and gold and copper, the substrate. In addition, the possibility of the appearance of oxide phases and other intermetallics were also checked. Analysis using the PDXL (Rigaku) program made it possible to match individual cards to the reflections and identify individual phases.

 

• P11, Line 333-334,

The formation of the needles in Fig. 4b and 4f is due to the intense hydrogen evolution upon the reduction as stated by the author. It is in contrast to the CV results in which HER does not occur after -0.6 V.

In paragraphs from lines 325 to 344, we describe coatings obtained at a potential of -0.7 V. Then, a significant increase in current was recorded on the voltammograms, indicating the hydrogen evolution reaction. In the sentence on lines 327-329, we indicate that the coatings are characterised by a different morphology than the coatings obtained at a potential of -0.6 V:

"The dendrites have different shapes and do not adhere so tightly to each other, as in the case of the needles obtained in the coatings (b) and (f) (Figure 4)."

I hope this sentence is understandable and was intended to show the significant difference between the coatings obtained at a potential of -0.5 (Figure 4 b and f) and the coating obtained at a potential of -0.7 V (Figure 4 c).

To increase the readability of the paragraph, we added a reference to Figure 4 c at the end of the sentence on line 326.

• The annealing process under Ar seems to have a great impact on morphology of the think film of Fig. 4c (vs. Fig. S2c). Is there any explanation to the observation?

The reviewer rightly pointed out the change in morphology after the annealing process for the coating obtained in a solution containing 0.004 M Pd + 0.008 Se M. The above layer contained the most selenium of all the deposited coatings. Selenium has a relatively low melting point and high vapour pressure compared to palladium. Nevertheless, according to the elemental analysis, there was no substantial change in the composition of the coating. So, we can exclude the process of evaporation of selenium. However, a phase transformation in the coating may have caused structural and morphological changes. The appearance of numerous peaks from the Pd17Se15 phase confirms this.

• What is the thickness of the PdxSey thin film?

Measuring the thickness of Pd-Se coatings is quite problematic. We tried to estimate the thickness of the coatings based on mass measurement. Assuming that the coating consists of pure selenium and palladium, the thickness of the coatings ranges from 1 to 4 μm. However, we believe the results are inaccurate enough to be published. In the future, we plan to study the cross-section of the coatings and, on this basis, estimate the coating thickness more precisely using scanning electron microscopy.

• What is the resulting pH value after the electrodeposition?

We measured pH after the electrolysis process, and the pH value always remained at 2 ±0.1. The stability of the bath meant that there was no need to use any buffers to keep it stable.

• The image resolution in Fig. 1 and 3 is poor. Resolution improvement is required.

The quality of the graphs have been improved.

• P5, Line 164, The anodic peak A1 -> The anodic peak A4?

There was an error on line 160, and the correct marking - A₄ - was inserted instead of the A₁

 

• P9, Line 263, Fig. 1a -> Fig. 3a?

In lines 259-260, the error was corrected, and a reference to the correct drawing was inserted - Fig. 3a

•  

An appropriate comment regarding the possibility of synthesising pd17Se15 has been added to the article.

Reviewer 4 Report

Comments and Suggestions for Authors

I've have read the manuscript entitled "Electrochemical synthesis of palladium selenides coatings" which can be publish some minors corrections.

first, some formatting corrections need to be made. For example line 132 ("error! ref not found) or line 157 (characters siez problem) etc...

Figure 3 must be redone. As it stands, it is not possible to distinguish the diffraction peaks and to have an opinion on the phases proposed by the authors. Authors must specify the deposit conditions . they increased the concentrations of Pd and Se, compared to the electrochemical study, which is justified but why did you choose these concentrations? What is the deposition time? Was there a choice made in relation to the number of coulomb for example? and have the authors looked at what influence the deposition time may have on the composition (and/or the phases)?

 

   

 

Author Response

Reviewer 4

I've have read the manuscript entitled "Electrochemical synthesis of palladium selenides coatings" which can be publish some minors corrections.

• first, some formatting corrections need to be made. For example line 132 ("error! ref not found) or line 157 (characters siez problem) etc...

The fonts and refences in the document were corrected

• Figure 3 must be redone. As it stands, it is not possible to distinguish the diffraction peaks and to have an opinion on the phases proposed by the authors. 

The quality of the graphs have been improved.

• Authors must specify the deposit conditions . they increased the concentrations of Pd and Se, compared to the electrochemical study, which is justified but why did you choose these concentrations? 

Electroanalytical studies were carried out at low concentrations due to the possibility of easy identification of peaks. An increase in concentration would result in an increase in peak intensity and peak size. Thus, the peaks would overlap, making voltammograms difficult to interpret.

Increasing the concentration of electrolytes in the deposition baths was intended to speed up the process of obtaining coatings. The proportions of the basic electrolyte components were kept the same as in the electrolytes used for electroanalytical studies.

• What is the deposition time? Was there a choice made in relation to the number of coulomb for example? and have the authors looked at what influence the deposition time may have on the composition (and/or the phases)?

The deposition time was 300 s. The optimal deposition time was chosen based on previous experiments. Electrolysis was carried out for times between 300 and 900 s. The composition of the coatings did not change with time, so the 300s time was used. A problem arose when the electrolysis time exceeded 900 s. This is when the coatings started to fall off the substrate. The above results were not included in the publication, as this would have significantly increased the volume of the manuscript.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I am satisfied with the revision. The paper is publishable in the present stage.