Effect of Copper Particle Size on the Surface Structure and Catalytic Activity of Cu–CeO₂ Nanocomposites Prepared by Mechanochemical Synthesis in the Preferential CO Oxidation in a H₂-Rich Stream (CO-PROX)

Round 1

Reviewer 1 Report

The manuscript by Zhigalina, Olga M. et al provides a mechanochemical strategy to make Cu-CeO2 catalysts for CO-PROX reaction. The manuscript could be accepted in present form.

If possible, I hope authors can answer my questions below:

1.     In Figure 11c, the O 1s spectra,  your sample may have carbonates and -OH groups. Authors should write more about it.

2.     Authors should run Raman experiments on these samples to bolster your conclusion about the oxidation state of Ce.

3.     In insitu FTIR, Cu cations should exhibit CO adsorption as well. Could authors also show the CO-Cu adsorption region to us.

4.     Authors should make a high resolution Fig. 15.

Normal English level

Author Response

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Reviewer 2 Report

This paper describes the effects of the particle size and morphology of Cu on the surface structure, physicochemical properties and catalytic activity of Cu-CeO₂ nanocomposites prepared by mechanochemical synthesis. The CO-PROX reaction mechanism was further studied. The results have shown that the surface structure of catalysts made of highly dispersed Cu powder is a key factor leading to their catalytic activity.

In the introduction, the authors mentioned that the reaction goes through a redox Mars-van Krevelen type mechanism. What is the reaction mechanism over the Cu-CeO₂ nanocomposites here for CO-PROX reaction? Please give some experimental results to illustrate the reaction mechanism.

There are conclusions about oxygen vacancy in the conclusions part, which can add the in situ Raman detection to be more persuasive;

It is suggested to increase the content of Ce³⁺ in Table 2, which could compare the oxygen vacancies;

The low temperature peak of H₂-TPR is related to the oxidation of H₂ by active oxygen species, which come from the two-dimensional Cu oxide structure on the surface of cerium oxide, and some of them come from the surface of cerium oxide. No literature has been cited and no evidence has been provided.

Our previous investigations were focused on the application of Cu/CuO–CeO2 com positions prepared by zero-waste mechanochemical synthesis as the catalysts for CO-PROX reaction. Please add the references. Also, some significant references on the CeO₂ for CO oxidation should also cite, like https://doi.org/10.1016/j.apsusc.2023.157438, https://pubs.acs.org/doi/10.1021/acscatal.0c03386.

Some other format problems, such as, 1) the authors should pay attention to the upper and lower scripts of ion symbols, such as the superoxide ion representation method on page 2. 2) The temperature unit in Figure 12 is suggested to be modified. 3) CO-PROX in the title and abstract should be given full name. 4) Most of the clarity of the picture is not enough, multiple pictures should be centered, the line can be appropriately bold; 5) Cu¹⁺ changed to Cu⁺

Author Response

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Reviewer 3 Report

This paper describes an original and interesting work. As such, it has the potential to be published in Catalysts. However, I have the following comments that the authors should carefully implement in the revised manuscript prior to publication.

1) In the revised manuscript, the authors should highlight that Cu-doped ceria is also useful in the field of environmental catalysis and, specifically, in diesel soot abatement or better the regeneration of (catalyst-coated) diesel particulate filters. In this regard, they should cite the following work: Topics in Catalysis, 2021, 64(3-4), pp. 256–269.

2) Introduction - The connection between the aim of the work and the literature gaps should be more deeply discussed, thus giving more strength to the reason for this work.

3) Results and Discussion/Conclusions - In the discussion, the practical impact of the results obtained in this work should be better highlighted. This should also be done in the section “Conclusions”.

4) Conclusions - More criticism is needed. The authors should also give a structured outlook on future research work.

I’m willing to review the revised manuscript.

Moderate editing of English language is required.

Author Response

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Round 2

Reviewer 2 Report

The authors need to pay attention to the mechanism. 

All the experiments I mentioned, the authors have not added during revision.  

Author Response

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Reviewer 3 Report

The authors have addressed my comments in a satisfactory manner. Overall, the manuscript has been improved after revisions. Therefore, it can be accepted for publication in Catalysts.

Minor editing of English language is required.

Author Response

Dear Reviewer,

Thank you very much for the help with improving our manuscript.