Rapid Photocatalytic Activity of Crystalline CeO2-CuO-Cu(OH)2 Ternary Nanocomposite
, Rajesh Kumar Manavalan 4, Shyju Thankaraj Salammal 1 and Nachimuthu Venkatesh 5Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors are recommended to review the nomenclature of chemical formulas
Are the authors sure of the catalysts concentration with the substrate? Because they propose 25 mg of catalyst per 50 mL of solution and then propose 20 mg/L, it is recommended to clarify this matter.
The authors propose that there is a presence of Cu(OH)2 in the materials. However, by XRD, there is a very low intensity of this material. Can you explain this situation in greater depth?
The authors are recommended to make an XRD measurement of Cu(OH)2 to contrast with the diffractograms made.
Can the authors further explain the low crystallinity presented by CeO2?
How can authors ensure that they have a homogeneous distribution by SEM, if they present an simply EDX? And how can they ensure the presence of CuO2 and Cu(OH)2?
The authors are recommended to perform SEM with EDX mapping, to know the distribution of the elements.
The band gap of the nanocomposite is not clear, why did they take that area? And not the previous zone, the same goes for the other two precursors.
Since the authors are proposing that there is Cu(OH)2 in the nanocomposite, it is recommended to take band gap measurements of this material as well.
The authors are recommended to perform XRF tests to determine nominal quantities of the elements present in the nanocomposite.
The authors are recommended to unify concepts related to discoloration and degradation.
The authors are recommended to perform TOC tests to determine the mineralization percentage of the substrates and determine if there is discoloration or degradation.
Authors are recommended to carry out material reuse cycles.
Author Response
Reviewers' comments:
Comments # 1
- The authors are recommended to review the nomenclature of chemical formulas
Response: We are very sorry for the mistake committed, we have reviewed the nomenclature of chemical formulas and changed in the revised manuscript.
- Are the authors sure of the catalysts concentration with the substrate? Because they propose 25 mg of catalyst per 50 mL of solution and then propose 20 mg/L, it is recommended to clarify this matter.
Response: Thanks for your valuable comments. The first one is catalyst concentration (25 mg /50 mL) and second one is dye solution concentration (20 mg/L) in water. The sentence revised and written as clearly in the revised manuscript.
- The authors propose that there is a presence of Cu(OH)2 in the materials. However, by XRD, there is a very low intensity of this material. Can you explain this situation in greater depth? The authors are recommended to make an XRD measurement of Cu(OH)2 to contrast with the diffractograms made.
Response: Thank you for the reviewer depth evaluation. Yes, authors agreed with reviewer statement. We observed a low intensity of the Cu(OH)2 because the precursor was equally distributed for the formation of the CuO and Cu(OH)2. In future, we will compare the bare samples with composite.
- Can the authors further explain the low crystallinity presented by CeO2?
Response: Thanks for the comments made. As per reviewer suggestion, we have strengthened the discussion and it is well known the lattice defect of CeO2 increase with decreasing particle size so the smaller particle size of CeO2 will lead to formation of surface lattice defect and generation of reactive oxygen species.
- How can authors ensure that they have a homogeneous distribution by SEM, if they present an simply EDX? And how can they ensure the presence of CuO2 and Cu(OH)2?
The authors are recommended to perform SEM with EDX mapping, to know the distribution of the elements
Response: Thanks for the comment made. Authors are agreed with above comments regarding SEM and EDX study. In the EDX result confirming the presence of element only. However, the samples (CuO and Cu(OH)2) are confirms by the XRD.. Unfortunately, we could not carry out the EDX mapping study at present situation. However, we will concentrate the EDX mapping in the work.
- The band gap of the nanocomposite is not clear, why did they take that area? And not the previous zone, the same goes for the other two precursors. Since the authors are proposing that there is Cu(OH)2 in the nanocomposite, it is recommended to take band gap measurements of this material as well.
Response: Thank you for reviewer’s careful examination. The area is removed. The band gap values are determined by simply from the absorption values. The advanced studies like ultraviolet photoelectron spectroscopy (UPS) will be concentrated in the future work.
The authors are recommended to perform XRF tests to determine nominal quantities of the elements present in the nanocomposite.
Response: We thank you for the suggestions and comments made further. Unfortunately, we were unable to conduct the XRF tests study at this time. However, we will prioritize XRF tests in future research.
- The authors are recommended to unify concepts related to discoloration and degradation.
Response: We thank you for the suggestions and comments made further. As per your comments we have compiled the results and strengthened the discoloration and degradation part and stated in the revised manuscript.
- The authors are recommended to perform TOC tests to determine the mineralization percentage of the substrates and determine if there is discoloration or degradation.
Response: Thanks for the comment, As per reviewer comment we have included TOC results to determine the degradation of pollutant and stated in the revised manuscript.
- Authors are recommended to carry out material reuse cycles.
Response: Thank you for reviewer’s comments. In the Fig.11 (b) we mention about the regeneration and reusability study of the nanocomposites. We found that the catalyst showed excellent stability and activity after the five cycles. Hence the skilled regeneration process is helpful to enhance the reusability up to 20 cycles
Reviewer 2 Report
Comments and Suggestions for AuthorsThis is an interesting paper addressing an important issue. It can be considered for publication in Sustainability. However, I have the following comments that the authors should carefully implement in the revised manuscript prior to publication.
1) Introduction - In order to give a more complete picture, the following work should also be briefly discussed: 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 better described, thus giving more strength to the reason for this work.
3) 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 - The authors should also give an outlook on future research work.
I’m willing to review the revised manuscript.
Comments on the Quality of English LanguageModerate editing of English language is required.
Author Response
Comments #2
This is an interesting paper addressing an important issue. It can be considered for publication in Sustainability. However, I have the following comments that the authors should carefully implement in the revised manuscript prior to publication.
- Introduction - In order to give a more complete picture, the following work should also be briefly discussed: Topics in Catalysis, 2021, 64(3-4), pp. 256-269.
Response: Thanks for the comments made. we have strengthened the introduction part we have added the novelty of the work in a clear manner in the revised version of the report. Further the relevant reference is cited in the revised manuscript. Thank you for given the opportunity.
- Introduction - The connection between the aim of the work and the literature gaps should be better described, thus giving more strength to the reason for this work.
Response: We thank you for the suggestions and comments made further. We have included the literatures according to your comments made in the revised manuscript.
The significance and the novelty of the work has been stated along with the previous reported literature as recommended and as been included in the introduction part in the manuscript in revised form.
- 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”.
- Conclusions - The authors should also give an outlook on future research work.
Response: Thank you for reviewer’s comments, as per your valuable suggestion we have added more key points for improve practical impact in the revised manuscript.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript prepared CeO2-CuO-Cu(OH)2 nanocomposite for photocatalytic degradation of pollutants. The nanocomposites were studied 29 their structural, morphology, optical and stability properties. In summary, the work is interesting and could be considered for publication in sustainability if the following questions are addressed.
(1) The composition corresponding to the diffraction peaks in the XRD patterns should be marked.
(2) Why the vertical axis was represented by (ahv)2 instead of (ahv)1/2 in the inset of Fig. 3? A reasonable explanation is needed. The reference may be helpful for this study (Chemical Engineering Journal 435 (2022) 135152).
(3) To further confirm the stability, the composition of recycled CeO2-CuO-Cu(OH)2 nanocomposite should be analyzed by some characterization, such as XRD, SEM, FTIR, and Raman.
(4) The electron transfer pathways between CeO2, CuO and Cu(OH)2 should be further discussed. The reference may be helpful for this study (Journal of Materials Chemistry A, 2020, 8, 4083-4090).
Author Response
Comments #3
The manuscript prepared CeO2-CuO-Cu(OH)2 nanocomposite for photocatalytic degradation of pollutants. The nanocomposites were studied 29 their structural, morphology, optical and stability properties. In summary, the work is interesting and could be considered for publication in sustainability if the following questions are addressed.
- The composition corresponding to the diffraction peaks in the XRD patterns should be marked.
Response: Thanks for the comment, As per reviewer comment we have included the most intense planes in the diffraction peaks (Fig.1) in the revised manuscript.
- Why the vertical axis was represented by (ahv)2 instead of (ahv)1/2 in the inset of Fig. 3? A reasonable explanation is needed. The reference may be helpful for this study (Chemical Engineering Journal 435 (2022) 135152).
Response: Thank you for reviewer’s comments, vertical axis label is presented in a correct format and we have cited a suitable reference in the revised manuscript.
- To further confirm the stability, the composition of recycled CeO2-CuO-Cu(OH)2 nanocomposite should be analyzed by some characterization, such as XRD, SEM, FTIR, and Raman.
Response: Thank you for the review suggestion. We have included the SEM and TEM images of the CeO2-CuO-Cu(OH)2 after five cycles. The identical morphology of the before and after treated samples is clearly shows high structural stability of the samples.
- The electron transfer pathways between CeO2, CuO and Cu(OH)2 should be further discussed. The reference may be helpful for this study (Journal of Materials Chemistry A, 2020, 8, 4083-4090).
Response: We thank you for the suggestions and comments made further. As per your suggestion, we have discussed the electron transfer pathways between the CeO2, CuO and Cu(OH)2 in the revised manuscript. Yes, the abovementioned reference helpful and it is cited the revised manuscript.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors responded adequately to the questions asked, so the article is suitable for publication.
Author Response
Comments # 1
- The authors are recommended to review the nomenclature of chemical formulas
Response: We are very sorry for the mistake committed, we have reviewed the nomenclature of chemical formulas and changed in the revised manuscript.
- Are the authors sure of the catalysts concentration with the substrate? Because they propose 25 mg of catalyst per 50 mL of solution and then propose 20 mg/L, it is recommended to clarify this matter.
Response: Thanks for your valuable comments. The first one is catalyst concentration (25 mg /50 mL) and second one is dye solution concentration (20 mg/L) in water. The sentence revised and written as clearly in the revised manuscript.
- The authors propose that there is a presence of Cu(OH)2 in the materials. However, by XRD, there is a very low intensity of this material. Can you explain this situation in greater depth? The authors are recommended to make an XRD measurement of Cu(OH)2 to contrast with the diffractograms made.
Response: Thank you for the reviewer depth evaluation. Yes, authors agreed with reviewer statement. We observed a low intensity of the Cu(OH)2 because the precursor was equally distributed for the formation of the CuO and Cu(OH)2. In future, we will compare the bare samples with composite.
- Can the authors further explain the low crystallinity presented by CeO2?
Response: Thanks for the comments made. As per reviewer suggestion, we have strengthened the discussion and it is well known the lattice defect of CeO2 increase with decreasing particle size so the smaller particle size of CeO2 will lead to formation of surface lattice defect and generation of reactive oxygen species.
- How can authors ensure that they have a homogeneous distribution by SEM, if they present an simply EDX? And how can they ensure the presence of CuO2 and Cu(OH)2?
The authors are recommended to perform SEM with EDX mapping, to know the distribution of the elements
Response: Thanks for the comment made. Authors are agreed with above comments regarding SEM and EDX study. In the EDX result confirming the presence of element only. However, the samples (CuO and Cu(OH)2) are confirms by the XRD.. Unfortunately, we could not carry out the EDX mapping study at present situation. However, we will concentrate the EDX mapping in the work.
- The band gap of the nanocomposite is not clear, why did they take that area? And not the previous zone, the same goes for the other two precursors. Since the authors are proposing that there is Cu(OH)2 in the nanocomposite, it is recommended to take band gap measurements of this material as well.
Response: Thank you for reviewer’s careful examination. The area is removed. The band gap values are determined by simply from the absorption values. The advanced studies like ultraviolet photoelectron spectroscopy (UPS) will be concentrated in the future work.
The authors are recommended to perform XRF tests to determine nominal quantities of the elements present in the nanocomposite.
Response: We thank you for the suggestions and comments made further. Unfortunately, we were unable to conduct the XRF tests study at this time. However, we will prioritize XRF tests in future research.
- The authors are recommended to unify concepts related to discoloration and degradation.
Response: We thank you for the suggestions and comments made further. As per your comments we have compiled the results and strengthened the discoloration and degradation part and stated in the revised manuscript.
- The authors are recommended to perform TOC tests to determine the mineralization percentage of the substrates and determine if there is discoloration or degradation.
Response: Thanks for the comment, As per reviewer comment we have included TOC results to determine the degradation of pollutant and stated in the revised manuscript.
- Authors are recommended to carry out material reuse cycles.
Response: Thank you for reviewer’s comments. In the Fig.11 (b) we mention about the regeneration and reusability study of the nanocomposites. We found that the catalyst showed excellent stability and activity after the five cycles. Hence the skilled regeneration process is helpful to enhance the reusability up to 20 cycles
Reviewer 2 Report
Comments and Suggestions for AuthorsThe 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 Sustainability.
Comments on the Quality of English LanguageModerate editing of English language is required.
Author Response
Comments #2
This is an interesting paper addressing an important issue. It can be considered for publication in Sustainability. However, I have the following comments that the authors should carefully implement in the revised manuscript prior to publication.
- Introduction - In order to give a more complete picture, the following work should also be briefly discussed: Topics in Catalysis, 2021, 64(3-4), pp. 256-269.
Response: Thanks for the comments made. we have strengthened the introduction part we have added the novelty of the work in a clear manner in the revised version of the report. Further the relevant reference is cited in the revised manuscript. Thank you for given the opportunity.
- Introduction - The connection between the aim of the work and the literature gaps should be better described, thus giving more strength to the reason for this work.
Response: We thank you for the suggestions and comments made further. We have included the literatures according to your comments made in the revised manuscript.
The significance and the novelty of the work has been stated along with the previous reported literature as recommended and as been included in the introduction part in the manuscript in revised form.
- 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”. Conclusions - The authors should also give an outlook on future research work.
Response: Thank you for reviewer’s comments, as per your valuable suggestion we have added more key points for improve practical impact in the revised manuscript.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors replied all the comments, and the revised manuscript is suitable for acception.
Author Response
Comments #3
The manuscript prepared CeO2-CuO-Cu(OH)2 nanocomposite for photocatalytic degradation of pollutants. The nanocomposites were studied 29 their structural, morphology, optical and stability properties. In summary, the work is interesting and could be considered for publication in sustainability if the following questions are addressed.
- The composition corresponding to the diffraction peaks in the XRD patterns should be marked.
Response: Thanks for the comment, As per reviewer comment we have included the most intense planes in the diffraction peaks (Fig.1) in the revised manuscript.
- Why the vertical axis was represented by (ahv)2 instead of (ahv)1/2 in the inset of Fig. 3? A reasonable explanation is needed. The reference may be helpful for this study (Chemical Engineering Journal 435 (2022) 135152).
Response: Thank you for reviewer’s comments, vertical axis label is presented in a correct format and we have cited a suitable reference in the revised manuscript.
- To further confirm the stability, the composition of recycled CeO2-CuO-Cu(OH)2 nanocomposite should be analyzed by some characterization, such as XRD, SEM, FTIR, and Raman.
Response: Thank you for the review suggestion. We have included the SEM and TEM images of the CeO2-CuO-Cu(OH)2 after five cycles. The identical morphology of the before and after treated samples is clearly shows high structural stability of the samples.
- The electron transfer pathways between CeO2, CuO and Cu(OH)2 should be further discussed. The reference may be helpful for this study (Journal of Materials Chemistry A, 2020, 8, 4083-4090).
Response: We thank you for the suggestions and comments made further. As per your suggestion, we have discussed the electron transfer pathways between the CeO2, CuO and Cu(OH)2 in the revised manuscript. Yes, the abovementioned reference helpful and it is cited the revised manuscript.
