Insight into the Effect of Oxygen Vacancy Prepared by Different Methods on CuO/Anatase Catalyst for CO Catalytic Oxidation
Round 1
Reviewer 1 Report
Novelty of the Work:
A new data about, the effectiveness of the CuO loaded on anatase TiO2 catalysts (CuO/Anatase) with oxygen vacancies were obtained.
Significance of the Work:
The authors show a new data for determination the reaction mechanisms of CO oxidation on various anatase surface, which offers detail insights of how to prepare suitable catalysts for low-temperature oxidation reactions.
Other Specific Comments:
Introduction - Despite the extensive references, the authors have to do more relevant discussion about the Cu-based catalysts
Experimental - The authors should included in purity of the used reactives.
Conclusions - The authors should give an outlook on future research work.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
10.12.2022
The revision of manuscript Catalysts-2100663 entitled:
“Insight into the effect of oxygen vacancy prepared by different 2 methods on CuO/Anatase catalyst for CO catalytic oxidation”
The manuscript describes a study on the preparation of CuO/anatase catalyst for CO oxidation and its comprehensive characterization with the special emphasis on the impact of reduction mode on oxygen vacancies and their role in creating of catalytic effect. The catalysts were synthesized using conventional technique of Cu deposition onto hydrothermally treated anatase via its impregnation with Cu(NO3)2 solution ant subsequent thermal treatment. The final step of preparation being the major element of the studies was reduction of CuO/Anatase system with H2 at 600 °C for 10 hours of with NaBH4 solution at room temperature. Materials differing in the preparation route were characterized with several techniques (ICP-OS, XRD, BET, TEM, EPR), and CO oxidation activity in wide range of temperature were compared. Authors found oxygen vacancies formed by CuO/Anatase reduction as the crucial factor creating high activity toward CO oxidation at relatively low temperature. It was also concluded that catalyst reduction with H2 provided more advantageous effect comparing to the reduction with NaBH4.
This work follows the scope of Catalysts journal. I found this paper interesting. Nevertheless, the manuscript has some shortcomings and inconsistency and need to be greatly improved to be publishable.
a) Idea of the studies
1. The idea of preparation technique seems doubtful since the stability of oxygen vacancies in the atmosphere of high oxidation potential is expected to be low. The explanation of oxygen vacancies creation by reduction as a the key part of the studies focused on CuO/Anatase catalysts to be effective in high-oxygen conditions should be explained in the introduction.
2. To reveal the effect of reduction on phys-chem properties and catalytic effect “in-situ” experiments are highly recommended. I have found no information concerning that issue. If the experiments were carried out “ex-situ” one may not exclude that oxygen vacancies created during reduction were partially reoxidized in air.
b) Preparation:
1. Cu(NO3)2 was used as CuO precursor. Was Cu(NO3)2 decomposition complete at 450 °C for 240 min?
2. One may expect a contamination of “CuO/Anatase-B” catalyst with Na due to using of NaOH and NaBH4 during preparation of the sample. What was the level of Na in final “CuO/Anatase-B” catalyst? What does the value pH=7 refers to (slurry, filtrate, others)?
3. Line 244: “… CuO/Anatase was added and dissolve it for 30 min.” – it seems “dissolve it” should be replaced with “dispersed slurry was mixed”.
4. The radical difference of hydrogen used for “CuO/Anatase-A” and “CuO/Anatase-B” is evident and obvious. Estimated molar ratio of HCuO/Anatase-A/HCuO/Anatase-B is ≈27. The reason of that should be explained.
c) Activity tests:
1. O2 content in reaction mixture should be verified since the value of 5% O2 was provided at Fig. 6. While the value of 20 % O2 was given in section 3.3.
2. The units convention should be kept in entire manuscript, e.g. units of mL/min or mlh-1 or sccm are currently used in case of gas flow.
d) Results
1. Table 1. – the Cu content in the samples is not clear since Cu content in CuO/Anatase-B and CuO/Anatase-H samples should be higher than in primary CuO/Anatase as a consequence of reduction causing partial oxygen removal. The opposite effect was observed by authors but its discussion was omitted.
2. Ln(r) vs. reciprocal temperature and Ea were shown in Fig. 6b – the method of “r” and Ea determination was not described in 3.3. section.
3. The value of the work would be increased if the issue of oxygen vacancies stability would be studied. One may not exclude that oxygen vacancies “disappear” during operation in oxygen-reach atmosphere especially at t>150 °C.
I hope that the authors will find my suggestions useful for resubmission.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Dear Authors,
In attachment you can find my comments about the manuscript.
Best regards
Comments for author File: Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I deeply went through the revised version and particularly author’s response to the comments and remarks. In my opinion sufficient statements and explanations were provided causing the discussion of results consistent.
Reviewer 3 Report
Dear Authors,
Thank you very much for the revision of the manuscript. Now, for me, the work is high quality study and it is ready to be published after the revision of the editorial office.
Best regards
