Optimization of SnPd Shell Configuration to Boost ORR Performance of Pt-Clusters Decorated CoOx@SnPd Core-Shell Nanocatalyst
, Wei Yeh 1, Amisha Beniwal 1, Che Yan 1, Kuan-Wen Wang 3, Po-Chun Chen 4, Xin Tu 2 and Tsan-Yao Chen 1,5,*
Round 1
Reviewer 1 Report
The present paper explores the possibilities of platinum based high performance catalysts with high utilization and low loading of Pt to improve the kinetics of the oxygen reduction reaction in fuel cells. This is achieved by creating clusters of Pt catalyst on the surface a core shell structure made of a Sn=Pd composite shell and a cobalt oxide core. The distribution of the Pt catalyst on the surface is shown to be dictated by the ratio of Sn/Pd in the particle surface layer and was found to have optimal performance at a ratio of 0.5. I found the paper to be interest, scientifically sound and well written other than the comments detailed below.
1. Line 46: Please provide references for platinum catalyst being the benchmark.
2. Line 86: Last paragraph of the introduction pretty much sums up the major conclusions of the paper. Authors are suggested to modify this to create a better transition from the existing literature to the scope of the present work.
3. Line 107: What makes the sequential wet chemical reduction method robust? Please clarify in the text.
4. Line 137: It is not immediately clear from the text that figure S1 is supplementary. Please clarify.
5. Figure 1: Need better labelling of all the pictures presented eg. red arrows and histograms. The conclusions based on the figures are not easily followed. Please modify for ease of understanding.
Author Response
October 31, 2022
Assistant Editor
Catalysts
Dear Referee
Thank you for your kind patience in waiting for our responses to the revision assignments by the reviewers. The attachment is the reference information for our submission and the responses to the referee’s comments.
Journal: Catalysts
Manuscript ID: catalysts- 1978484
Title: " Optimization of SnPd Shell Configuration to Boost ORR Performance of Pt-Clusters Decorated CoOx@SnPd Core-Shell Nanocatalyst"
Author(s): Mingxing Cheng, Dinesh Bhalothia, Wei Yeh, Amisha Beniwal, Che Yan, Kuan-Wen Wang, Po-Chun Chen, Xin Tu, Tsan-Yao Chen *
We have properly responded to the revision comments and revised the manuscript accordingly.
If you have any concerns or more additional materials are required, please do not hesitate to contact me. I will be happy to provide it.
Sincerely yours,
Tsan-Yao Chen
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The submitted manuscript deals with the performance of Pt-clusters decorated CoOx@SnPd core-shell nanocatalyst for oxygen reduction reaction (ORR). The main task of the work is the optimization of SnPd shell configuration for the improvement of the catalyst’s activity towards ORR. The results are collected and presented properly. There are some shortcomings concerning mainly the manuscript organization, references, and partly the results presentation. From a scientific point of view, the presented results are mostly satisfactory, with a few missing data. The manuscript can be accepted for publication after a major revision according to the comments given below.
Manuscript organization – please follow the Instruction for the Catalysts papers organization. The section Material and Methods is missing. It should be added at the end of the manuscript. The main description of the Methods explored and conditions should be extracted from the Supplementary and given in this section. Also, chemicals used should be given in this Section.
The title 2. Experimental procedures should be removed and the part related to the synthesis: “Synthesis of Pt-clusters Decorated CoOx@SnPd Core-Shell Nanocatalysts” should be given in the beginning of the section Results and Discussion, as subsection 2.1. The other subsections should also be numbered ( 2.1; 2.2; etc).
References – Although previous work from the authors is relevant and should be cited, with respect to the overall number of references these comprised almost 50% of cited references. It is necessary to expand the reference list to involve the up-to-date references from the other authors.
Citing references – the reference number(s) should be given before a period in the sentence, not after. For instance: p.1. line 42, instead of “…power applications.[1-2]”, there should be “…power applications [1-2].” Correct throughout the paper.
Labeling of catalysts- It is hard for a reader to follow the labeling as given in the text, for instance: CSPP 1005 etc. Instead, they could be labeled according to their stoichiometry, taking into account the chemical symbols and the ratio between the metals.
Labeling of the potentials for H ads/des; Hads or Hdes should be written as subscripts- not superscripts: EHads, EHdes, etc.
XRD-results- as an important result it should be moved from Supplementary to the main text together with the description and discussion. The orientations should be provided in the Figure for each peak.
Cyclic voltammetry – Figure 3 – yellow area should be described in the text
ORR- Tafel slope (from the activation control region in the polarization curve), and the overall number of electron exchanged (from K-L plots) should be provided.
Comparison- The results obtained in this work should be compared with the relevant results from the other authors.
Supplementary- 2. Electrochemical Analysis - In the first sentence: “… the catalyst ink was made by dispersing 5mg as-prepared catalyst powder in a solution containing 1mL of isopropanol and 50μL of Nafion-117…”
– the total volume of the solution should be given.
Comments for author File: Comments.pdf
Author Response
October 31, 2022
Referee
Catalysts
Dear Referee
Thank you for your kind patience in waiting for our responses to the revision assignments by the reviewers. The attachment is the reference information for our submission and the responses to the referee’s comments.
Journal: Catalysts
Manuscript ID: catalysts- 1978484
Title: " Optimization of SnPd Shell Configuration to Boost ORR Performance of Pt-Clusters Decorated CoOx@SnPd Core-Shell Nanocatalyst"
Author(s): Mingxing Cheng, Dinesh Bhalothia, Wei Yeh, Amisha Beniwal, Che Yan, Kuan-Wen Wang, Po-Chun Chen, Xin Tu, Tsan-Yao Chen *
We have properly responded to the revision comments and revised the manuscript accordingly.
If you have any concerns or more additional materials are required, please do not hesitate to contact me. I will be happy to provide it.
Sincerely yours,
Tsan-Yao Chen
Author Response File: Author Response.pdf
Reviewer 3 Report
This manuscript by Cheng et al describes the synthesis of Pt-Clusters decorated CoOx@SnPd core-shell nanocatalyst (CSPP) for oxygen reduction reaction under an alkaline solution. Several CSPP catalysts with different Sn/Pd ratios were synthesized. The morphology of the catalysts was analyzed by HRTEM while the chemical environment of the platinum was analyzed by X-ray absorption spectroscopy (XAS).
My biggest criticism concerning this paper is the treatment of the palladium as a supporting element and not as a catalyst by itself. Palladium is a well-known catalyst for ORR in alkaline solutions -
https://doi.org/10.1021/jacs.1c08644 J
https://doi.org/10.1016/j.elecom.2015.12.016
What is the purpose of lowering the platinum content while using even more expensive metal? Palladium is a rare metal and by all definitions considered a precious group metal (its market value is even higher than that of platinum). The observed catalytic activity is not only from the platinum, but it is also (and probably mostly, considering the low loading of Pt) coming from the palladium. All the kinetic parameters (mass activity etc.) should be normalized to the total content of Pt + Pd, not just platinum. The author didn’t report the palladium content which does not allow a real assessment of the catalytic activity. A simple way to prove this point is to synthesize the catalysts without any platinum and to compare it to the platinated catalysts.
Putting aside, there are many papers of palladium and platinum catalysts (separately) under alkaline conditions with much better performances. Not just that, PGM-free catalysts, which are much cheaper, are usually even better than the PGM catalysts in alkaline solutions. The only possible advantage could have been seen in fuel cell measurements but the author didn’t conduct any.
In short, the author proposes a more complicated and expensive synthesis, with overall more precious metals (palladium + platinum) which results in an inferior catalyst in comparison to PGM-free catalysts.
In addition, there are also several comments regarding the methodology-
1. The weight content of the palladium, platinum, cobalt, and Tin for each catalyst should be given, preferably in a table.
2. Please specify the catalysts loading for the RDE measurements.
3. What is the surface area of the RDE electrode? Please also present the RDE graph in the current density unit.
4. The counter electrode was a Pt wire. It is highly unconventional to use it as a counter electrode since there is no control over the potential of the electrode which might result in the dissolution of platinum from the counter and redeposition on the working electrode. Please use a carbon-based electrode (preferably glassy carbon) or use a separate compartment with a ceramic separator.
5. Line 248:” Accordingly, the oxide reduction peak (EOdes) for CSPP 1005 NC is shifted to the highest potential among all the NCs, implying the lowest energy for ORR facilitations and thus highest ORR performance as compared to CSPP 1010 and CSPP 1020 NCs.”
Even if we are accepting the assumption that it is “directly related to the ORR Performance of NCs”, following this logic the Pt commercial catalyst should be better since the onset potential for the EOdes is higher than CSPP 1005 NC.
6. For direct assessment of the catalyst’s performance, the RDE measurements of the catalysts without platinum and a catalyst without palladium and platinum (only cobalt and tin) should also be presented.
Author Response
October 31, 2022
Referee
Catalysts
Dear Referee
Thank you for your kind patience in waiting for our responses to the revision assignments by the reviewers. The attachment is the reference information for our submission and the responses to the referee’s comments.
Journal: Catalysts
Manuscript ID: catalysts- 1978484
Title: " Optimization of SnPd Shell Configuration to Boost ORR Performance of Pt-Clusters Decorated CoOx@SnPd Core-Shell Nanocatalyst"
Author(s): Mingxing Cheng, Dinesh Bhalothia, Wei Yeh, Amisha Beniwal, Che Yan, Kuan-Wen Wang, Po-Chun Chen, Xin Tu, Tsan-Yao Chen *
We have properly responded to the revision comments and revised the manuscript accordingly.
If you have any concerns or more additional materials are required, please do not hesitate to contact me. I will be happy to provide it.
Sincerely yours,
Tsan-Yao Chen
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors' responses are satisfactory. The manuscript is improved and ready for publication.
Author Response
The authors appreciate the kind acknowledge of our efforts by the referee.
Reviewer 3 Report
I will address each comment as shown in the author’s response letter.
Comment 1: Since Pd is a precious metal, I would add a bar graph showing the mass activity when considering the total mass of the precious metals (Pd+Pt). This is a fair comparison to the commercial Pt/C. You can add this graph to the SI.
Comment 2: In any case, a table with the exact composition of each catalyst in weight percentage (metals and carbon content) is crucial. There is no simple way to understand what the actual loading of the Pt and other metals is. The molar ratio is not enough information. Not reporting (or knowing) the exact composition of your catalysts make this report very problematic. You can also use atomic adsorption or XRF to determine the composition of the metals.
Comment 6: This is true when you compare the peak position, but it is clear that the onset for Pt/C is at more positive potential than that of CSPP 1005. This is also following the RDE graph where it can be seen that the ORR onset for the Pt/C is higher than that of CSPP 1005. Kinetically, CSPP 1005 might be better than Pt/C which causes the high mass activity, but your argument is referring to the onset potential for the Eods. In other words, the EOds starts at a more positive potential than CSPP 1005.
Author Response
The point-by-point response to the referee comments are addressed in the attached file.
Author Response File: Author Response.pdf
