Study of the Cathode Pt-Electrocatalysts Based on Reduced Graphene Oxide with Pt-SnO₂ Hetero-Clusters

Round 1

Reviewer 1 Report

OK, now

 

Minor, the English language

 

Reviewer 2 Report

The author presented some interesting work on catalyst degradation based on ESA. However, I think the work is incomplete and some of the data do not support the claims sufficiently. I suggest a major revision on the present work. 

1. The last sentence of the abstract is rather ambiguous. The author should rephrase it to convey the message clearer. What does the author refer to with "similar activity value" but "greater ESA value"? Is it "similar activity value" by weight, ESA, or geometric surface area? If it is "similar activity value" but "greater ESA value", is the author suggesting that the specific activity for the catalyst has decreased? 

2. It is better for the author to be consistent in the nomenclature. In some sections, the materials are stated as "platinum" and "tin dioxide", while in others they are stated as "Pt" and "SnO2". 

3. It is unclear which of the peaks in Figure 4 XRD is attributed to RGO (002), as there appear to be 3 peaks between 20-30 degrees. 

4. L60, is the author referring to Hummer's method or Hammer's method? 

5. How does the author verify that c-RGO has amorphous carbon deposited on graphene layer from Figure 1? It is also possible that the carbon is in the form of small crystallites in nanometer scale. 

6. The words in Figure 2 FFT images are not legible. I suggest the author to change the colour of the fonts to improve the contrast. 

7. The EXAFS data in table 2 is inconclusive and the author seems to be over-interpreting the data. First of all, it is extremely difficult to differentiate the contributions of Pt-Pt (2.76A) and Pt-Sn (2.84A), hence reducing the reliability of the interpretation. Secondly, it seems unreasonable to have total coordination number of more than 12 for Pt (sum of Pt-Pt and Pt-O first shells). Based on the current data, I am not convinced the data supports the claim that Sn is incorporated into the Pt structure. I suggest repeating the measurement on the Sn edge for verification or provide high resolution EDX data from TEM. 

8. The author should include k-space figures to help readers verify the EXAFS data. 

9. Although electrode degradation is important, it will also be critical to evaluate the actual performance of the catalysts. I suggest the author to provide the polarisation curves of the catalysts, especially the benchmark reference catalysts, for comparison, in addition to the normalised ESA after AST. 

10. It will be helpful to perform XPS analysis on the catalyst to evaluate the electronic interactions between Pt and Sn, as this forms part of the author's claims on the function of SnO2 protection layer. 

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

This paper is written in a rather weak manner. The novelty of this study is not clear. Even starting with the abstract, it only contains generalities, this is not the essence of the work. Are the techniques specified in the abstract useful, if the conclusion of these characterization techniques is not identified, or if the novelty derived from these techniques is not specified? In my opinion, the work is just a laboratory study, but without the pretense of being translated into an article  

 

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

In this paper, the Pt²⁰/SnO₂¹⁰/c-RGO with Pt-SnO₂ hetero-clusters was prepared as an electrocatalyst for oxygen reduction reaction. The as-prepared catalyst exhibits good catalytic activities and stability attributed to the synergistic effects of Pt-SnO₂ hetero-clusters and c-RGO support. This work is valid for the publication. However, before its publication, there are still some issues to be addressed as follows:

1.          It is difficult to identify the inset images in Fig. 2c and Fig. 2f. The authors should provide higher quality images.

2.          The authors should provide the distribution of C element in Fig. 3.

3.          The phases and the corresponding PDF cards of different catalysts should be provided in Fig. 4. Besides, which phase does the diffraction peak located at 70°correspond to? The authors should give explanations.

4.          How did the authors confirm the formation of Pt-SnO₂ heterostructure in Pt²⁰/SnO₂¹⁰/c-RGO? The authors should give more evidence.

5.          The ¢sample obtained by chemical reduction (c-RGO) is more characterized by the presence of amorphous carbon¢ is mentioned in the manuscript. The authors should provide HRTEM images of c-RGO and t-RGO to confirm this point.

6.          Will the structure and morphology of Pt²⁰/SnO₂¹⁰/c-RGO maintain stable after AST? The authors should provide the corresponding XRD pattern and TEM image of Pt²⁰/SnO₂¹⁰/c-RGO after AST.

7.          The ¢average particle size of platinum is 2.1 nm (Pt²⁰/SnO₂¹⁰/c-RGO) and 2.7 nm (Pt²⁰/SnO₂¹⁰/t-RGO)¢ is mentioned in the manuscript. The authors should give explanations.

The authors should clarify and emphasize the active sites in the Pt²⁰/SnO₂¹⁰/c-RGO catalyst.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors have addressed the comments reasonably. I am fine with the present work being published. 

Author Response

Thank you for improving the manuscript.

Reviewer 3 Report

The changes made do not describe the novelty; in my opinion this paper  still remains only a laboratory study. The application is not clear. The electrochemical characterization is not done professionally, the description of the method is missing from the experimental part. Why was the evaluation done in both sulfuric acid and perchloric acid? However, the comparison is not justified, only the data are presented, without a proper explanation.  

 

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

In the revised manuscript, the authors fully addressed my concerns. Therefore, I recommend this work for publication in Inorganics.

Author Response

Thank you for improving the manuscript.

Round 3

Reviewer 3 Report

The improvement is really poor, as well the the quality of discussions. The study is not "detailed" as it's mentioned in the introduction. Thus, do it scientifically.