Comparison of the Mechanisms of deNOx and deN2O Processes on Bimetallic Cu–Zn and Monometallic Cu–Cu Dimers in Clinoptilolite Zeolite—A DFT Study Simulating Industrial Conditions
Round 1
Reviewer 1 Report
The manuscript explores the denOx and dN2O processes in bimetallic zeolite using density functional theory (DFT). The authors aim to elucidate the reaction mechanism by analyzing various intermediates and transition states. They argue that water presence in the system is advantageous as it facilitates -OH preadsorption, which proves beneficial for both deNOx and deN2O processes. Specifically, Cu-O-Cu and Cu-O-Zn bimetallic systems are studied in clinoptilolite zeolite. The results indicate that Cu-O-Zn is suitable for the deNOx process, while Cu-O-Cu is preferable for the deN2O process. However, the presence of -OH benefits both cases.
Based on my assessment, I do not recommend this paper in its current form for publication in Catalyst. It requires thorough revisions of the methodology, model, and writing to enhance its suitability. Please find my detailed comments below:
- Introduction: The introduction is excessively long, and lacks focus on the current work. It includes an extensive discussion on vanadium tungsten species, which is unnecessary. I recommend rewriting the introduction to provide a clear understanding of the significance of the deNOx/deN2O process and the role of zeolites in catalysis. Avoid overwhelming readers with excessive details and maintain a concise and coherent narrative.
- Computational Details (Page 3): The basis sets used in the calculations are unclear. The notation "Si and Al (6321/521/1)" requires clarification. To enhance clarity, I suggest using standard names, such as DZVP, TZVP, TZVPP, or 6-31G(d,p), which are more widely recognized in the field.
- Geometric Models: I have concerns regarding the model cluster used for the calculations. Figure 1 does not depict a confined pore, which is a critical aspect of zeolite catalysis. The selection of this model cluster needs clarification. Has this type of model been employed in previous literature on zeolite catalysis? I recommend referring to the article by Li et al (ACS Catal. 2019, 9, 11, 10279–10293) for a more efficient zeolite model cluster.
- System Charge and Oxidation States: When Cu-O-Cu or Cu-O-Zn is placed in zeolite, what overall charge is considered for the system? Additionally, what are the oxidation states of Cu and Zn in this system? Providing this information will enhance the understanding of the electronic properties of the studied system.
- Figure 4 and Figure 5: The highly exothermic nature of the A1 and B1 formation (with a binding energy of 2.81 eV or 64 kcal/mol) appears unreasonable for physisorption. I recommend that the authors carefully review their computational methods or benchmark their results against another functional/basis set to ensure accuracy.
- Figure 4: I find it challenging to comprehend the process depicted by TS2. Multiple bond-breaking and bond-making events occurring in a single step should not pass through a single transition state. To facilitate a clear understanding for readers, it would be beneficial to provide a movie or animation of A3-TS2-A5 and similar steps.
- Figure 6: Is there a transition state (TS) between C2 and C3? If so, it should be included in the figure and discussed in the text to ensure the completeness of the analysis.
- Figure 8b and Figure 11b: Please clarify the distinctions between Figure 8b and Figure 11b to help readers.
- Figures 15 and onwards: It is advisable for the authors not to include all the optimized structures in the main text. Presenting a large number of optimized structures within the main text increases the article's length and disrupts its flow. Instead, I recommend including the most relevant and representative structures while moving the remaining structures to supplementary material or an appendix.
In its current form, the manuscript requires thorough revisions before it can be considered for publication. The method, model, and writing need careful reconsideration to ensure suitability. Taking these measures will significantly improve the manuscript's quality and increase its chances of being published in a platform.
The English language needs editing through out the manuscript.
Author Response
Dear Reviewer,
We are appreciate for all comments and suggestions, which we followed accordingly.
With kind regards,
Izabela Czekaj
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors focus on the mechanisms of deNOx and deN2O processes, and detailed discuss the catalysts: a clinoptilolite zeolite catalyst with deposited Cu-Cu monometallic dimer and Cu-Zn bimetallic dimer with bridged oxygen between the metal atoms.
In order to Understand the reaction principles of these catalysts, the manuscript can add the introduction of the catalysts and reaction activity.
Author Response
Dear Reviewer,
We are appreciate for all comments and suggestions, which we followed accordingly.
With kind regards,
Izabela Czekaj
Author Response File: Author Response.pdf
Reviewer 3 Report
In the manuscript “Comparison of the mechanisms of deNOx and deN2O processes on bimetallic Cu-Zn and monometallic Cu-Cu dimers in clinoptilolite zeolite - a DFT study simulating industrial conditions”, the authors have used DFT calculations to examine the performance of deNOx and deNO2 process on monometallic Cu-Cu dimer and bimetallic Cu-Zn with bridged oxygen between the metal atoms. The calculation results seem interesting and worth further exploration. The followings are suggestions/comments for the manuscript.
Comments
1. The language is poor and sometimes hard to understand. It should be checked by a native speaker.
2. For the model where 5T cluster was chosen, why do you choose this model without considering other alternatives?
3. In section 3.4, you explained the changes among bond length, orders, as well as charges, what is your conclusion?
4. Catalytic activity: Even if correct, how do the computed results translate into expected catalytic performance? Again, it is common today to perform a kinetic analysis.
5. At the end of Discussion, "the active site CuOZn in clinoptilolite zeolite in deNOx process is more reactive than the analogous site in the FAU (0.45 eV) and MFI (0.75 eV) zeolite", can you explain what causes this phenomenon?
The language is poor and sometimes hard to understand. It should be checked by a native speaker.
Author Response
Dear Reviewer,
We are appreciate for all comments and suggestions, which we followed accordingly.
With kind regards,
Izabela Czekaj
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I am delighted with the authors' revisions. They have meticulously addressed my concerns, offering lucid explanations with ample supporting citations. Moreover, they have diligently incorporated the suggested changes into the manuscript, including the reduction of the introduction part as recommended by the reviewer. Based on the current state of the article, I am confident that it is now well-prepared for publication in Catalysts.
Author Response
Dear Reviewer,
We are again appreciate to Reviewer 1 for exceptional help to improve our paper before publication. Additionally we agree with Academic Reviewer that our answer to point 5 of Review 1.
With kind regards,
Izabela Czekaj
Author Response File: Author Response.pdf
