Forming a Cu-Based Catalyst for Efficient Hydrogenation Conversion of Starch into Glucose
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis manuscript investigated the synergistic action of hydrothermal catalyst and reduced catalyst based on Cu in the hydrogenation conversion of starch to glucose. Additionally, optimal reaction conditions for the reduced catalyst Cu/Al2O3 were determined. The catalyst based on Cu0 exhibited performance outstanding compared with other catalysts as well evaluated in this work. Although the manuscript could be interesting for a broad readership of catalytic community the authors need to pay attention to the following issues.
Major corrections.
The results in both characterizations (XRD and XPS) show that there are presently more than metallic cooper as shown in Figure 1 (a) and Figure 4 (d). However, the authors fit their discussion with the argument that there is only one phase of (Cu0) when the results show that there is more than one phase (different oxidation state of Cu in XPS results). The characterization (XRD and XPS) of the catalyst reduced was not well assessed. Most likely because after the catalyst was reduced its measure in XRD and XPS was not immediately leading to a partial oxidation of the metallic copper. I suggest that once the reduction process ends stock the catalyst in a vial under argon atmosphere to delay the oxidation of the sample and make the XRD and XPS assessment as soon as possible. The authors have to make again the XRD and XPS characterizations of the catalyst-reduced Cu/Al2O3 avoiding the partial oxidation of the sample at the moment of XRD and XPS assessment. I expect that the results of XRD and XPS change show the complete reduction of cooper in the catalyst Cu/Al2O3, if it does not, the author has to rewrite the abstract, discussion, and conclusions.
Minor corrections
1. I recommend placing the section on Materials and Methods before the section on Results and Discussion as usually appears in the article on catalysis.
2. What is the percentage weight of Cu present in the catalyst? The authors need to indicate in the section on preparation of materials.
3. I am not sure if the word baked in section 4.2 is appropriate, instead the authors could use dried or heated.
4. In section 4.3 in line 323 the authors mentioned the core level of Ru 3d and Ru 3p, but ruthenium was not used instead was use copper, is that correct? . If so, correct it.
5. Generally, in the articles about catalysis the amount of catalysts used in the reaction is expressed in percentage of weight. So I suggest to do it.
6. In section 4.4. How do the authors ensure that the catalyst is reduced at the conditions of 90-120°C and hydrogen pressure between 1 to 4 MPa? It is not necessary a higher temperature than 400°C to reduce Cu. Add a reference that describes the reduction of a cooper at the conditions used in this work.
7. In line 93 is incomplete the information. The peaks at 43.3, 50.4, and 74.1 ° are ascribed a plane of what phase?
8. There is a mistake in the information in line 98. The JCPDS 86-1410 is from theta alumina and not from gamma alumina as the authors mentioned. See the next reference (https://doi.org/10.3390/ma14195465). So correct the text and figure 1 a respectively.
9. In the XRD pattern of the Cu/Al2O3 sample in not clear the peaks associated with the Cu phase as occur with CuO and Al2O3 phases are. The authors need to add symbols or lines inset the XRD pattern to clarify each phase. Otherwise in the XRD pattern of Cu/Al2O3 shows that there is also cooper as CuO and not only Cu0 as the authors mentioned. The figure 1 a should be redrawn to achieve concise and clear effect.
10. What does mean “DD” in the legend of the X axis in Figure 1 c? The authors should write it as Pore Diameter or PD.
11. The authors mentioned that the decrease in specific surface area and pore diameter when the catalyst was reduced can be attributed to the Electrostatic action of Cu to make part of the surface pores blocked. However, the authors need to add references that support that explanation. On the other hand, I wondering if after reduction process the structure of alumina partially collapse leading to decreasing surface area and pore diameter. So the authors need to be deep in the explanation in this part.
12. The resolution of the micrograph (figure 2 (d)) is poor and also the resolution scale cannot be distinguished in both images (figures 2 c and d). The figure 2 (d) should be changed. Otherwise, when the authors mention in line 123 “which is in accordance with the conclusion of Figure 1(c).” 17. It is not clear what was the conclusion of Figure 1 c. The authors need to rewrite and give a reasonably explanation about the decreasing in particle size after the reduction process in order to clarify the idea.
13. Based on Figure 3 in lines 139 and 140 there are mistakes, Figure 3(c) does not correspond to Al 2p as well Figure 3 (d) does not associated to Cu 2p
14. In line 143 the word as-catalyst is repeated twice
15. In the first paragraph of the XPS discussion the authors have to assign the five peaks present in the Cu 2p core level. There are three species of copper present in the catalyst. So what are those species?
16. In the O1s core level, why there is not a band assigned to the CuO species? I wondering if the band at 532 eV could be related to CuO species. It is important to know that if copper oxide is present in the sample, the oxygen of CuO have to appear in the core level O1s. The discussion of XPS results have to be redone. I suggest to use works in the literature and NIST X-ray Photoelectron Spectroscopy to Database to assigned the XPS signals properly.
17. Concerning XPS results from the catalyst reduced, I arise the next question. How much time passed between the catalyst being reduced and the XPS assessment?, since is evident in the XPS core level Cu 2p (Figure 4 d) there are present more than one Cu species with different oxide states and not only one species associated with Cu0 as it is mentioned.
18. In line 181 do you have any explanation about the decreasing yield while the reaction pressure increases?
19. Figure 5 needs to be modified since the title and the values of the axes ca not be distinguished, beside in Figure 5 d one value of catalyst dosage (2.25 g) is missing.
20. It strikes me that in all different conditions (Figure 5) the maximum value of starch yield was the same 83.18%. Are you sure that there were no differences in the starch yield?
Comments on the Quality of English Language
Grammar and syntax in the text have been improved
Author Response
Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Paper Title” (ID: 2847222). These comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. All changes in the main text are highlighted in yellow, and the point-by-point responses to all your comments are listed below:
Reviewer #1's comments:
Comments and Suggestions for Authors
This manuscript investigated the synergistic action of hydrothermal catalyst and reduced catalyst based on Cu in the hydrogenation conversion of starch to glucose. Additionally, optimal reaction conditions for the reduced catalyst Cu/Al2O3 were determined. The catalyst based on Cu0 exhibited performance outstanding compared with other catalysts as well evaluated in this work. Although the manuscript could be interesting for a broad readership of catalytic community the authors need to pay attention to the following issues.
Major corrections.
The results in both characterizations (XRD and XPS) show that there are presently more than metallic cooper as shown in Figure 1 (a) and Figure 4 (d). However, the authors fit their discussion with the argument that there is only one phase of (Cu0) when the results show that there is more than one phase (different oxidation state of Cu in XPS results). The characterization (XRD and XPS) of the catalyst reduced was not well assessed. Most likely because after the catalyst was reduced its measure in XRD and XPS was not immediately leading to a partial oxidation of the metallic copper. I suggest that once the reduction process ends stock the catalyst in a vial under argon atmosphere to delay the oxidation of the sample and make the XRD and XPS assessment as soon as possible. The authors have to make again the XRD and XPS characterizations of the catalyst-reduced Cu/Al2O3 avoiding the partial oxidation of the sample at the moment of XRD and XPS assessment. I expect that the results of XRD and XPS change show the complete reduction of coper in the catalyst Cu/Al2O3, if it does not, the author has to rewrite the abstract, discussion, and conclusions. Minor corrections.
Response: We highly appreciate your constructive comments that help us improve the quality and raise the impact of our manuscript. We have followed your valuable suggestions and subjected the manuscript to a revision in abstract, discussion, and conclusion section, and revisions were highlighted in yellow.
Comments 1: I recommend placing the section on Materials and Methods before the section on Results and Discussion as usually appears in the article on catalysis.
Response: Thank you very much for the kind comment. Research articles have a standard structure, which is set out in the instructions for authors of the journal and the journal template. The majority of journals use a so-called IMRAD structure, meaning that the sections are Introduction, Materials and Methods, Results, and Discussions. Some journals such as catalysts, moles of MDPI require a Conclusions section at the end, and others have the Materials and Methods section after the Results and Discussions. So, we have not revised paper structure.
Comments 2: What is the percentage weight of Cu present in the catalyst? The authors need to indicate in the section on preparation of materials.
Response: Thank you for your valuable suggestions. the percentage weight of Cu present in the catalyst has been added in the section on preparation of materials and the revisions were highlighted in yellow.
Comments 3: I am not sure if the word baked in section 4.2 is appropriate, instead the authors could use dried or heated.
Response: Thank you for your professional comments. Your suggestions have been adopted and word “bake”has been modified, the revision was highlighted in yellow.
Comments 4: In section 4.3 in line 323 the authors mentioned the core level of Ru 3d and Ru 3p, but ruthenium was not used instead was use copper, is that correct? If so, correct it.
Response: Thank you for your valuable suggestions. There is indeed a spelling mistake line 323，We have modified it, which has been marked in yellow.
Comments 5: Generally, in the articles about catalysis the amount of catalysts used in the reaction is expressed in percentage of weight. So, I suggest to do it.
Response: Thank you very much for this remark. Your suggestions have been adopted and the amount of catalysts has been converted into percentage of weight, the diagram has been modified accordingly, and the revisions were highlighted in yellow.
Comments 6: In section 4.4. How do the authors ensure that the catalyst is reduced at the conditions of 90-120°C and hydrogen pressure between 1 to 4 MPa? It is not necessary a higher temperature than 400°C to reduce Cu. Add a reference that describes the reduction of a cooper at the conditions used in this work.
Response: Thank you very much for professional remark. First, the catalyst in this study was indeed reduced in situ. I have also read some literature on Cu-based catalysts, for example doi.org/10.1016/j.fuel.2023.130432, doi.org/10.1039/D3CY01064C.their reduction condition is around 200℃, 2 MPa for 2 h. The catalyst was reduced in https://doi.org/10.1002/jctb.6508 at condition of 120 ℃, 2 MPa for 1 h. Moreover, there are also some paper in situ reduction, such as doi.org/10.1016/j.mcat.2020.111298, doi.org/10.3390/su122410601, and so on.
Comments 7: In line 93 is incomplete the information. The peaks at 43.3, 50.4, and 74.1 ° are ascribed a plane of what phase?
Response: Thank you for your valuable suggestions. Your suggestions have been adopted and the peaks at 43.3, 50.4, and 74.1 ° are ascribed a plane of Cu metal, and the revisions were highlighted in yellow.
Comments 8: There is a mistake in the information in line 98. The JCPDS 86-1410 is from theta alumina and not from gamma alumina as the authors mentioned. See the next reference (https://doi.org/10.3390/ma14195465). So correct the text and figure 1 a respectively.
Response: Thank you for your remark, your suggestion has been adopted, and the revisions were highlighted in yellow.
Comments 9: In the XRD pattern of the Cu/Al2O3 sample in not clear the peaks associated with the Cu phase as occur with CuO and Al2O3 phases are. The authors need to add symbols or lines inset the XRD pattern to clarify each phase. Otherwise in the XRD pattern of Cu/Al2O3 shows that there is also cooper as CuO and not only Cu0 as the authors mentioned. The figure 1 a should be redrawn to achieve concise and clear effect.
Response: Thank you for your remark. Your suggestions have been adopted and the Figure has been revised with yellow marked.
Comments 10: I What does mean “DD” in the legend of the X axis in Figure 1 c? The authors should write it as Pore Diameter or PD.
Response: Thank you very much for your remark. Your suggestions have been adopted, and the revisions were highlighted in yellow.
Comments 11: The authors mentioned that the decrease in specific surface area and pore diameter when the catalyst was reduced can be attributed to the Electrostatic action of Cu to make part of the surface pores blocked. However, the authors need to add references that support that explanation. On the other hand, I wondering if after reduction process the structure of alumina partially collapse leading to decreasing surface area and pore diameter. So, the authors need to be deep in the explanation in this part.
Response: Thank you very much for your professional remark. Firstly, in terms of γ-Al2O3, the γ-Al2O3 phase is formed upon the dehydration of aluminum oxyhydroxide boehmite at temperatures ranging from 400 to 700 °C by calcination. It is particularly noteworthy that the BET surface areas and pore volume increases with the increase of calcination temperature(https://doi.org/10.1021/la0361767). The calcination temperature of the catalyst prepared in this experiment is 500 ℃, so it cannot cause structural collapse.
Finally, About the question of “the decrease in specific surface area and pore diameter when the catalyst was reduced can be attributed to the electrostatic action of Cu to make part of the surface pores blocked”, we have added literature support[i].
(Yang X.; Erickson L.; Hohn K., et al. Sol-Gel Cu-Al2O3 Adsorbents for Selective Adsorption of Thiophene out of Hydrocarbon. Industrial &Engineering chemistry Research 2006, 45: 6169-6174.)
Comments 12: The resolution of the micrograph (figure 2 (d)) is poor and also the resolution scale cannot be distinguished in both images (figures 2 c and d). The figure 2 (d) should be changed. Otherwise, when the authors mention in line 123 “which is in accordance with the conclusion of Figure 1(c).” 17. It is not clear what was the conclusion of Figure 1 c. The authors need to rewrite and give a reasonably explanation about the decreasing in particle size after the reduction process in order to clarify the idea.
Response: Thank you very much for your remark. Your suggestions have been adopted, and the resolution of scale has been revised, and explanation about the decreasing in particle size has explanation again and highlighted in yellow.
Comments 13: Based on Figure 3 in lines 139 and 140 there are mistakes, Figure 3(c) does not correspond to Al 2p as well Figure 3 (d) does not associate to Cu 2p.
Response: Thank you for your valuable suggestions. Your suggestions have been adopted, and The discussion section has been slightly revised.
Comments 14: In line 143 the word as-catalyst is repeated twice.
Response: Thank you very much for your remark. Your suggestions have been adopted, and the repeated word “as-catalyst” has been deleted.
Comments15: In the first paragraph of the XPS discussion the authors have to assign the five peaks present in the Cu 2p core level. There are three species of copper present in the catalyst. So what are those species?
Response: Thank you very much for your remark. Your suggestions have been adopted, and the revisions were highlighted in yellow.
There are representative peaks of Cu 2p3/2 (933.7 eV) and Cu 2p1/2 (953.6 eV), the BE peaks observed for Cu 2p represent CuO. While the characteristic Cu2+ satellite peaks are observed at 941.3 eV, 943.5 eV and 962.2 eV, respectively, which are a result of hybridization between 3d Cu orbital and the oxygen 2p orbital[ii]
(i Singh R.; Kundu K.; Pant K K. CO2 Hydrogenation to Methanol over Cu-ZnO-CeO2 Catalyst: Reaction Structure–Activity Relationship, Optimizing Ce And Zn Ratio, And Kinetic Study. Chemical Engineering Journal 2024, 479: 147783.)
Comments 16: In the O1s core level, why there is not a band assigned to the CuO species? I wondering if the band at 532 eV could be related to CuO species. It is important to know that if copper oxide is present in the sample, the oxygen of CuO have to appear in the core level O1s. The discussion of XPS results have to be redone. I suggest to use works in the literature and NIST X-ray Photoelectron Spectroscopy to Database to assigned the XPS signals properly.
Response: Thank you for your professional suggestions. Your suggestions have been adopted, and the revisions were highlighted in yellow.
According to previously reference[iii] , the lowest binding energy corresponds to lattice oxygen (Oα) in mixed metal oxide, the medium binding energy is assigned to surface-adsorbed oxygen (Oβ) species, and the higher binding energy is attributed to surface hydroxyl species (Oγ). Here, three peaks centering at 529,5eV(Oα), 531.0 eV (Oβ), and 532 eV (Oγ) are assignable to lattice oxygen (Al-O, Cu-O), chemical adsorbed oxygen and adsorbed water[iv].
(ii Ostovar S.; Moussavi G.; Mohammadi S., et al. Rapid degradation of Omeprazole and highly effective inactivation of E. coli in the UVA-light photocatalytic process with Cu-doped in spinel-structured ɣAl2O3 as a stable catalyst. Chemical Engineering Journal 2024, 479: 147536.)
Comments 17: Concerning XPS results from the catalyst reduced, I arise the next question. How much time passed between the catalyst being reduced and the XPS assessment? Since is evident in the XPS core level Cu 2p (Figure 4 d) there are present more than one Cu species with different oxide states and not only one species associated with Cu0 as it is mentioned.
Response: Thank you very much for your professional remark. First of all, thank you very much for raising this question, which will be a qualitative improvement for my future scientific research. After you raised questions about XRD and XPS characterization for more than one times, I rediscussed the XRD and XPS characterization according to your requirements, and actually made some new discoveries. The reduced catalyst sealed with high purity N2 was delivered. In the case of hydrogenation, copper oxide is first in situ reduced to cuprous oxide, and then reduced to Cu. It may be that the reduction temperature in this experiment is not very high, so there are cuprous oxide and copper in the reduction products (EQ1). This is also found in the XRD characterization of Cu/Al2O3. Based on the above reasons, we have revised the figure, results, discussion, summary and conclusion accordingly.
(EQ1)
Figure 4
Comments 18: In line 181 do you have any explanation about the decreasing yield while the reaction pressure increases?
Response: Thank you very much for your professional remark. Firstly, the conversion rate of starch increased and the selectivity of glucose also increased under the pressure range between 1 and 1.8 MPa, So, the glucose yield gradually increases with increasing pressure, this effect was due to the increased concentration of dissolved hydrogen in water at higher pressures, which causes greater adsorption of starch on the surface of the Cu/Al2O3 catalyst. At a reaction pressure of 1.8 MPa, the highest glucose yield was obtained, due to the maximum solubility of hydrogen in water and the resulting optimal catalytic effect. However, when the pressure reached above 2.0 MPa, hydrogen maybe continue to reacting with glucose to produce products such as glycerol and ethylene glycol, etc, resulting in a decrease in the yield of glucose. Such as Cellulose (2018) 25:2259–2272, https://doi.org/10.1007/s10570-018-1721-7.
Comments 19: Figure 5 needs to be modified since the title and the values of the axes ca not be distinguished, beside in Figure 5 d one value of catalyst dosage (2.25 g) is missing.
Response: Thank you very much for your remark. Your suggestions have been adopted, and the revisions were highlighted in yellow.
Comments 20: It strikes me that in all different conditions (Figure 5) the maximum value of starch yield was the same 83.18%. Are you sure that there were no differences in the starch yield?
Response: Thank you for your professional suggestions. First of all, I think this is a probability problem in the experimental setting, that is, the conditions I optimized at the beginning are the optimal process conditions. As can be seen from the abrupt catalytic dose in Figure 5, 2.25 is not what I originally wanted to add, but after adding it, this catalytic dose is indeed the optimal one.
[[i]] Yang X.; Erickson L.; Hohn K., et al. Sol-Gel Cu-Al2O3 Adsorbents for Selective Adsorption of Thiophene out of Hydrocarbon. Industrial &Engineering chemistry Research 2006, 45: 6169-6174.
[[ii]]. Singh R.; Kundu K.; Pant K K. CO2 Hydrogenation to Methanol over Cu-ZnO-CeO2 Catalyst: Reaction Structure–Activity Relationship, Optimizing Ce And Zn Ratio, And Kinetic Study. Chemical Engineering Journal 2024, 479: 147783.
[[iii]]. Ostovar S.; Moussavi G.; Mohammadi S., et al. Rapid degradation of Omeprazole and highly effective inactivation of E. coli in the UVA-light photocatalytic process with Cu-doped in spinel-structured ɣAl2O3 as a stable catalyst. Chemical Engineering Journal 2024, 479: 147536.
[[iv]]. Wang X.; Chong J.; Liang S., et al. Contributions of Mn-Doping in Cuo/Al2O3 Sorbent for Enhancement of H2S Removal at Low and Wide Temperature Range. Fuel 2023, 334: 126546.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe article portrays the preparation of a catalyst for glucose production. The introduction is well-executed and does not need improvement, as it effectively explains the context of the work, showcasing various other methods for glucose production and highlighting the positive and negative aspects of these methods.
Some questions and comments on the article for improvement before subsequent publication:
1) Shouldn't the XPS drift line be corrected promptly during data processing? It's not common to represent it that way.
2) The caption for Figure 5 needs correction: uppercase letter in the initial.
3) Why were those dimensions chosen for preparing the material? Do you check this problematic?
4) Why is there an optimum in the Figure 3d)? Could it be an indicator of diffusion problems?
5) What are the future steps in this research? Could this be placed before the conclusion?
Author Response
Dear reviewer
Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Paper Title” (ID: 2847222). These comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. All changes in the main text are highlighted in yellow, and the point-by-point responses to all your comments are listed below:
Reviewer #2's comments:
The article portrays the preparation of a catalyst for glucose production. The introduction is well-executed and does not need improvement, as it effectively explains the context of the work, showcasing various other methods for glucose production and highlighting the positive and negative aspects of these methods.
Some questions and comments on the article for improvement before subsequent publication:
Response: Thank you very much for your positive feedback and constructive comments that have improved the clarity and raised the impact of our manuscript. We have very carefully studied your comments and subjected the manuscript to a minor revision. We sincerely hope that we have adequately accounted for all your concerns by intensive discussion. All changes in the main text are highlighted in yellow, and the point-by-point responses to all your comments are listed below:
Comments 1: Shouldn't the XPS drift line be corrected promptly during data processing? It's not common to represent it that way.
Response: Thank you very much for your professional comments. Some quantitative results have been added to the abstract and revisions were highlighted in yellow. The standard peak position of elemental carbon (generally taken as 284.8 eV) minus the measured peak position of elemental carbon (284.6 eV)
equals the charge correction value Δ (0.2 eV). Some peaks may have larger deviations, but in general, the peak positions should differ by no more than 0.5 eV. If the difference is too large, it is necessary to consider whether there is a problem with the calibration. So, the XPS drift line has not been corrected during data processing in our paper.
The standard peak position of elemental carbon
Comments 2: The caption for Figure 5 needs correction: uppercase letter in the initial.
Response: Thank you very much for the kind comment of reviewer. The initial has been revised in Figure 5 and revisions were highlighted in yellow.
Comments 3: Why were those dimensions chosen for preparing the material? Do you check this problematic?
Response: Thank you for your professional comments. we would like to discuss the dimensions of catalyst material forming from two aspects. Firstly, a good catalyst should have a large specific surface area, high activity, and good stability. Using aluminum oxide (Al2O3) with a larger specific surface area as a carrier can increase the specific surface area of the catalyst, thereby enhancing its activity. Secondly, the use of copper (Cu) as an active component in hydrogenation for starch applications is considered from both experimental and industrial perspectives. Therefore, we consider the process of pellet formation to prepare catalyst.
Comments 4: Why is there an optimum in the Figure 5d)? Could it be an indicator of diffusion problems?
Response: Thank you for your valuable comments. The optimum in the Figure 5 (f) indeed examines the impact of diffusion on glucose yield during starch hydrogenation.
Comments 5: What are the future steps in this research? Could this be placed before the conclusion?
Response: Thank you very much for this remark. In the future steps in this research, we will investigate the process of CuO/Al2O3 catalyzing starch hydrogenation to glucose on a fixed bed.
Author Response File: 
Author Response.docx
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors need to describe in the Catalyst Characterizations section the procedure realized to characterize the reduced sample by XRD and XPS (see your response to comment 17 and be more descriptive) to avoid possible misunderstanding. After that, the revised manuscript can be accepted for publication.
Comments on the Quality of English LanguageThe English is acceptable
Author Response
Dear reviewer
Thank you very much for your positive feedback and constructive comments that have improved the clarity and raised the impact of our manuscript (ID: 2847222). We have very carefully studied your comments and subjected the manuscript to a major revision. All changes in the main text and supplementary information are highlighted in pink, and the point-by-point responses to all your comments are listed below:
Reviewer #1's comments:（round 2）
Comments and Suggestions for Authors
This manuscript investigated the synergistic action of hydrothermal catalyst and reduced catalyst based on Cu in the hydrogenation conversion of starch to glucose. Additionally, optimal reaction conditions for the reduced catalyst Cu/Al2O3 were determined. The catalyst based on Cu0 exhibited performance outstanding compared with other catalysts as well evaluated in this work. Although the manuscript could be interesting for a broad readership of catalytic community the authors need to pay attention to the following issues.
Response: We highly appreciate your positive evaluation of our work and are grateful for your constructive feedback that helps us improve the quality of the manuscript.
- The authors need to describe in the Catalyst Characterizations section the procedure realized to characterize the reduced sample by XRD and XPS (see your response to comment 17 and be more descriptive) to avoid possible misunderstanding. After that, the revised manuscript can be accepted for publication.
Response: Thank you very much for your careful reading and corrections. We have followed your advice and the revisions were highlighted in pink.
Author Response File: Author Response.docx
