Point-Defect-Rich Carbon Sheets as the High-Activity Catalyst Toward Oxygen Reduction and Hydrogen Evolution
Round 1
Reviewer 1 Report
The manuscript is well organized and rich in experimental data. The results are also quite interesting as the performances of this material are notable.
Experiments adequately support conclusions.
The paper does not contain errors or weak points and therefore its publication in this form is recommended.
Author Response
We appreciate the reviewer’s comments.
Reviewer 2 Report
Comments to the Author
The manuscript addresses electrocatalysis of proton and dioxygen reduction by carbon based materials. The catalytic performances are interesting and seem promising, and most (vide infra) of the characterizations have been performed. Unfortunately however, the paper, as it is, fails to make an important contribution to the literature in the field of electrocatalysis. I understand that product characterization is tedious for ORR (but is performed using RRDE), but for HER a simple GC experiment could provide a Faradaic yield for those materials. This is not shown in the present study. As far as I am concerned, it is mandatory to report product (here H2) characterization in a catalytic paper, furthermore in a journal named “Catalysts”. I could retract my review if those data are shown by the authors.
I have several remarks and questions:
1. p. 2, line 57. References are needed to support this statement.
2. I was very puzzled by the choice of the authors to present first the electrocatalytic results before the characterization of the prepared materials. It would be wise to reverse the order.
3. p. 3, caption of figure 2. I have read the manuscript and the caption of this figure several times, but I do not understand the experimental difference(s) between figure 2a and 2b. I am missing something?
4. p. 3, lines103-106. Bubbles evolution is not an accurate measure of the HER and does not indicate the rate of the catalytic reaction. This sentence and the figure S3 are then unnecessary.
5. p. 4, lines122-125. Those measures are showing 18 % and 36 % decrease of the catalytic activity of alkaline and acidic media, which is far from a “superior durability in long-term electrochemical hydrogen evolution process”.
6. p. 4, 2nd paragraph. The measurement of the ECSA is not appropriate for PDRC-800 and PDRC-900 as figures S5a and S5b do not show flat current (unlike PDRC-1000). So a comparison of those values is not possible.
7. p. 7, line 196-198. A reference is needed for the sentence “Density functional theory … defects-rich structure.”
8. p. 8, section 3.2. A yield of the material production would be informative. The synthesis is started with 50 g of calcium gluconate, how much is left at the end?
9. SI, p. 2. Some references have not been changed into numbers (line72 and line 76-77).
In summary, this paper attempts to contribute to the ORR and HER fields, but due to the lack of H2 characterization and the other comments reported above, it does not have the appropriate quality to be published in the journal Catalysts.
Author Response
Attached please find our response
Author Response File: 
Author Response.pdf
Reviewer 3 Report
1) The present work shows an in-depth study of the electrocatalytic activity of materials based on C modified by N. However, there is no clear evidence of the role of Ca impurities that the authors inevitably formed during synthesis. It is not reported how much Ca remains after preparation. This point must be absolutely clarified and represents the flaw of the manuscript.
2) The quantification of the different types of N present on the samples is missing, which can be done by the XPS analysis of the N1s. This parameter is not well discussed in the part of the conclusions. Despite being the key point to explain the different electrocatalytic activities.
3) The extensive use of acronyms makes reading difficult, I recommend limiting them. I would put a summary table of the samples used and their main properties (name, treatment, surface area, content of N etc ...). This especially in the initial part, otherwise I can't understand what you're talking about.
4) I also recommend using the same colors for the same sample in the different figures, to help the reader read: for example always green for PDRC-1000.
Based on these considerations, a majour review of the work is required prior to publication. Especially considering the first point indicated.
Author Response
Attached please find our response
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors addressed most of my comments and corrections from my first review. Nevertheless they do not provide dihydrogen characterization, and to my view this is not appropriate. Most (unfortunately not all) papers published in this field are showing H2 detection, and this is to me mandatory. Thus I do not recommend publication in the journal Catalysts.
Reviewer 3 Report
Most of the required revision have been improved, therefore the manuscript can be accepted for publication.
