The Interaction Mechanism Between Modified Selective Catalytic Reduction Catalysts and Volatile Organic Compounds in Flue Gas: A Density Functional Theory Study
and Bing Zhang 2
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
In this project, the authors investigated the binding property of VOCs over metal doped V2O5-TiO2 surfaces. The results is interesting and I would like to recommend publication as long as the following issues are well addressed:
- In section 3, Materials and Methods, the authors should also cite the source of GGA PBE functional, the PAW method and the DFT+D3 van der waals correction. Also, the authors are supposed to mention the the which surface of TiO2 are using like 110 or 001? The periodic TiO2 surface super cell would be disclosed as well. (e.g., 2*2 or 3*3).
- Usually, when deal with the transition metal oxides, DFT+U correction would be a popular way to handle the strongly correlated 3d electrons. Could the authors explain why they didn’t apply DFT+U?
- As for the adsorption structure in Figure 1 and 2, the authors mainly focus on the physical adsorption, normally, the carbon would bind with the surface oxygen like V-O-V or V=O to form the chemical adsorption. Could the authors disscuss the chemical adsorption as well?
- The coordination number of the metal atoms like V and other transition metals can greatly affect the reactivity. Could the author also discuss on that?
- The resolution of PDOS plot in Figure 4 is not enough, could the authors replace with the high resolution figure?
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript describes the seria of calculation of molecules of two types (acetone and toluene) adsorbed by TiO2 surface modified by metal-vanadium oxide, where metal are Mn, Mo, W or Ni. Author found that mixtures V-Mn and V-Ni are better adsorbants than other. This could be an interesting result, but the models are quite simple which may neglect it applicability.
Major comments:
1. Authors claim on the chemical bonding between molecules and surface, which is pretty doubtful due to high distances between them. Judging from the given images, I suggest a van-der-Waals (vdW) bonding type. The high adsorption energies are explained by many vdW bond contacts (Cads - Osurf, etc). The image with charge difference (CCD) - can be explained a polarization of molecules and surface, not by transfer of electron from surface to molecule. The density of states show tiny contributions of molecule's p-states of C.
2. The structure of presentation is poor. Seems like Materials and methods section was moved to the end of text without altering of Result and Discussion section. This prohibits the smooth reading. Please add paragraph with model description in the result section
Minor comments:
3. Methods are not described. What energy cutoff was used, how it was selected for different species? What was the sampling of Brullion Zone? Why so small model of surface was used? The vacuum was 12 A, so that the width of the model in x and y direction shoaled be so, to diminish lateral interactions. How CCD, COHP etc values were obtained? How adsorbate energy was calculated? Why ICOHP missing the units (eV), may be it is not ICOHP?
4. Please mark the position of Fermi energy on plots. Only a few eV around it (even below) are the utter importance. Also please improve the quality of the figures. In particular, some COHP plots are smooth, other - not. Why?
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors
The overall efficiency of combining denitrification and volatile organic compound (VOCs) removal through selective catalytic reduction (SCR) technology is currently mainly limited by the VOCs removal aspect. However, the existing researches have focused on the experimental study of de-VOCs, ignoring the study of the microscopic mechanism of the interaction between VOCs and catalysts, which failed to provide a theoretical basis for the further optimization of catalysts. Therefore, this work explored the microscopic interaction mechanisms between SCR catalysts doped with different additives and typical VOCs (acetone and toluene) in flue gas based on density functional theory calculations. By comparing the adsorption energies on V2O5-TiO2 surfaces doped with different transition metals, it was found that Mn- and Ni doped surfaces exhibited excellent interactions with acetone and toluene. Electronic structure analysis revealed that the VMn-TiO2 and VNi-TiO2 surfaces exhibited more intense orbital hybridization with acetone and toluene, which promoted charge transfer between the two and resulted in stronger interactions. In addition, the analysis of temperature on adsorption free energy showed that VMn-TiO2 and VNi-TiO2 still maintained high activity at high temperatures. This work contributes to clarifying the interaction mechanism between SCR and VOCs and enhancing the VOCs removal efficiency.
Comments to the author:
-The abstract is too long. Please shorten it and include the main results with numerical values for comparative purposes.
-Comparison of present results with the results of other similar investigations need to be provided.
-Some strong correlation should be provided between the reported results and experimental results or already reported data.
-Formulas an definitions of calculated parameters not provided.
-Desorption temperatures/properties should be evaluated/discussed.
-The band gap for adsorbed systems may be interesting to elucidate.
-I suggest citing the following papers to contextualize the present work with similar DFT studies with adsorbed molecules.
https://doi.org/10.1021/acs.jpcc.8b09811
https://doi.org/10.1016/j.ica.2023.121596
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe quality of the paper has been greatly improved and the paper could be published to Catalysts.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe discussion on the distinguishing between covalent or van-der-Walls bond type is probably beyond the scope of the manuscript, so, I recommend to publish it though the interatomic distances look more like van-der-Walls ones.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have adequately addressed the queries raised in the revision, and the article is now suitable for publication.
