CeO2-Supported TiO2−Pt Nanorod Composites as Efficient Catalysts for CO Oxidation
Round 1
Reviewer 1 Report
1. Please insert superiority of the prepared catalyst over some reported catalysts for a model reaction in a Table.
2. What is the results of oxidation reaction in the presence of only TiO2 or CeO2 or without the catalyst? Please clarify in the manuscript.
3. What is the results about the reusability of the synthesized catalyst? Please clarify in the text.
4. What is the role of each part of the catalyst in oxidation of CO? Please explain in detail with some experimental tests and literature references.
5. The intensity of the Raman peaks are very low. Please check the Raman spectra and improve them.
Author Response
Dear Reviewer:
Thank you for your comments concerning our manuscript entitled “Enhanced catalytic performance of CeO2 supported TiO2-Pt nanorod in CO oxidation” (ID: molecules-2198344). Those comments are valuable and very helpful for revising and improving the manuscript, as well as the important guiding significance to our researches. According to the reviewers’ detailed suggestions, we have made a careful revision on the original manuscript. The revised are marked in yellow in the manuscript. The main corrections and the responds to the reviewers’ comments are as follows.
Response to reviewers’ comments:
Referee #1
Comment 1: Please insert superiority of the prepared catalyst over some reported catalysts for a model reaction in a Table.
Response: Thanks for reviewer’s kind suggestion very much. We have compared the catalytic performance of (0.5TiO2-Pt)/CeO2 with the state of art TiO2/CeO2-based catalysts reported in literature, as shown in Table S1, indicating its superior catalytic property.
Comment 2: What is the results of oxidation reaction in the presence of only TiO2 or CeO2 or without the catalyst? Please clarify in the manuscript.
Response: Thanks for reviewer’s question. We have tested the oxidation reaction of pure CeO2, and concluded that the T50 and T99 of pure CeO2 is 235 °C, 320 °C, respectively, as observed in Figure S4.
Comment 3: What is the results about the reusability of the synthesized catalyst? Please clarify in the text.
Response: Thanks for reviewer’s question. The catalytic performance of (0.5TiO2-Pt)/CeO2 keeps stable after three repeated tests, implying good reusability of (0.5TiO2-Pt)/CeO2, as provided in Figure S5.
Comment 4: What is the role of each part of the catalyst in oxidation of CO? Please explain in detail with some experimental tests and literature references.
Response: Thanks for reviewer’s question. We think the outstanding catalytic performance of (TiO2-Pt)/CeO2 catalyst can be attributed to the unique structure and phase composition. The existence of Ce3+ on catalytic interface can adsorb active oxygen, which is conducive to the formation of interfacial active center; highly dispersed TiO2 can accelerate the migration rate of active oxygen species on the surface of CeO2 so that the oxygen atoms can react with activated CO to form CO2, which can be demonstrated from the reported CeO2 and TiO2 based literatures, like Nanotechnology 28(4) (2017) 045602, Journal of Hazardous Materials 403 (2021) 123630.
Comment 5: The intensity of the Raman peaks are very low. Please check the Raman spectra and improve them.
Response: Thanks for reviewer’s question. We have retested the Raman characterization and reanalyzed the raman data, see Fig. 6.
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and frame work of the manuscript. And here we did not list the changes but marked in blue in the revised. We appreciate Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval. Once again, thank you very much for your comments and suggestions. Best wishes,
Sincerely yours!
Reviewer 2 Report
1. Abstract, the authors should give the background of this study, for example, the major challenge and problem of catalytic CO oxidation should be stated.
2. Introduction Section should be revised to add some more strong points for the motivation of this work, and to summarize the recent advances and the main challenge of this field.
3. I suggest the authors supplement some characterizations about material redox property, such as H2 TPR, or some reaction mechanism tests, such as TPD, in situ FTIR, or some theory calculations.
4. Section 2.2, the discussions about performance and should be revised, and combined with previous characterization result.
5. Fig. 8b, was that a DFT result? Did any characterization and result can support this figure?
Author Response
Dear Reviewer:
Thank you for your comments concerning our manuscript entitled “Enhanced catalytic performance of CeO2 supported TiO2-Pt nanorod in CO oxidation” (ID: molecules-2198344). Those comments are valuable and very helpful for revising and improving the manuscript, as well as the important guiding significance to our researches. According to the reviewers’ detailed suggestions, we have made a careful revision on the original manuscript. The revised are marked in yellow in the manuscript. The main corrections and the responds to the reviewers’ comments are as follows.
Response to reviewers’ comments:
Referee #2
Comment 1: Abstract, the authors should give the background of this study, for example, the major challenge and problem of catalytic CO oxidation should be stated.
Response: Thanks for reviewer’s kind suggestion very much. We have added this part of content in Abstract part. “Supported Pt-based catalysts have been identified as highly selective catalysts for CO oxidation, but their potential for applications has been hampered by the high cost and scarcity of Pt metals as well as aggregation problems at relative high temperatures”.
Comment 2: Introduction Section should be revised to add some more strong points for the motivation of this work, and to summarize the recent advances and the main challenge of this field.
Response: Thanks for reviewer’s kind suggestion. We have revised these points and also supplied the recent advances of related works, like “Liou’s team (J Hazard Mater 403 (2021) 123630) prepared Cu-doped TiO2 microsphere for catalytic CO oxidation. They think the highly dispersed doping metals can increase the exposure of copper and TiO2 matrix, thus benefiting for improvement of catalytic performance. However, the bulk metal oxides always show poor charge transfer ability and conductivity, which hinders their full play. Combing TiO2 with Pt is an effective strategy to avoid the aggregation of Pt and enhance the overall property of materials.” Please see the highlighted contents in Introduction part.
Comment 3: I suggest the authors supplement some characterizations about material redox property, such as H2 TPR, or some reaction mechanism tests, such as TPD, in situ FTIR, or some theory calculations.
Response: Thanks for reviewer’s question. We have added the characterizations about the catalytic activity of (0.5TiO2-Pt)/CeO2 under different space velocities as well as the catalytic performance under varied oxygen concentrations, see Fig. 8. The catalytic performance of (0.5TiO2-Pt)/CeO2 as a function of flow rate at 70 °C is detected, with corresponding shown in Fig. 8a. As the total gas flow rate increases from 40 to 120 ml min-1, the CO conversion decreases from 97% to 58%. It can be also clearly detected that the reaction rate is positive related to flow rate. Fig. 8b further explores the influence of O2 concentration in feed gas on catalytic performance of (0.5TiO2-Pt)/CeO2. The test temperature is kept at 90 °C with flow rate100 mL min-1. The CO conversion rate can reach 99% as 10% O2 is initially infused into the system thanks to the sufficient O2 environment; CO conversion rate is reduced first and then kept stable at 10% when O2 supply is suddenly decreased to zero, which may be ascribed to the existence of surface lattice oxygen that can migrate to active sites and combine with adsorbed CO to form oxygen vacancies. However, CO conversion rate increases in poor oxygen condition (0.3-5% O2) and then recovers to initial 99% value and keeps unchanged when O2 is resupplied into feed gas, implying superior catalytic CO oxidation property of (0.5TiO2-Pt)/CeO2.
Comment 4: Section 2.2, the discussions about performance and should be revised, and combined with previous characterization result.
Response: Thanks for reviewer’s question. We have tested the reusability of (0.5TiO2-Pt)/CeO2 and concluded that the catalytic performance of (0.5TiO2-Pt)/CeO2 keeps stable after three repeated tests (Figure S5), implying good reusability of (0.5TiO2-Pt)/CeO2. The catalytic activity of (0.5TiO2-Pt)/CeO2 also surpasses the state of art TiO2/CeO2-based catalysts reported in literature, as shown in Table S1, indicating its superior catalytic property.
Comment 5: Fig. 8b, was that a DFT result? Did any characterization and result can support this figure?
Response: Thanks for reviewer’s question. Fig. 8 (Fig. 9 after revision) is not a DFT result, it is a possible mechanism for reaction of CO on (TiO2-Pt)/CeO2 catalyst. The reaction mechanism is concluded based on experiment and published literatures. Hopefully you will be satisfied with our explanation.
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and frame work of the manuscript. And here we did not list the changes but marked in blue in the revised. We appreciate Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval. Once again, thank you very much for your comments and suggestions. Best wishes,
Sincerely yours!
Reviewer 3 Report
Reviewer’s Comments:
The manuscript “Enhanced catalytic performance of CeO2 supported TiO2-Pt nanorod in CO oxidation” is a very interesting work. In this work, the nanorod structured (TiO2-Pt)/CeO2 catalysts with addition of 0.3 at% Pt and different atomic ratio of Ti were prepared through a combined dealloying and calcination method. XRD, XPS, SEM, TEM and STEM measurements were used to confirm the phase composition, surface morphology and structure of synthesized samples. After calcination treatment, Pt nanoparticles were semi-inlayed on the surface of CeO2 nanorod and TiO2 were highly dispersed into the catalyst system, resulting in formation of (TiO2-Pt)/CeO2 with high specific surface area and large pore volume. The unique structure can provide more reaction path and active sites for catalytic CO oxidation, thus contribute to generation of catalysts with high catalytic activity. The results are consistent with the data and figures presented in the manuscript. While I believe this topic is of great interest to our readers, I think it needs major revision before it is ready for publication. So, I recommend this manuscript for publication with major revisions.
1. In this manuscript, the authors did not explain the importance of the nanorod morphology in the introduction part. The authors should explain the importance of nanorod morphology.
2) Title: The title of the manuscript is not impressive. It should be modified or rewritten it.
3) Correct the following statement “The outstanding catalytic performance is ascribed to the stable structure and proper TiO2 doping as well as combined effect of Pt and TiO2. The research results are of importance for further development of high catalytic performance nanoporous catalytic materials”.
4) Keywords: There so many keywords and reduce them up to 5. So, modify the keywords.
5) Introduction part is not impressive. The references cited are very old. So, Improve it with some latest literature like 10.1016/j.chemosphere.2022.133772, 10.1016/j.eurpolymj.2021.110783
6) The authors should explain the following statement with recent references, “The O 1s spectrum in Figure 2d can be fitted to three peaks”.
7) Add space between magnitude and unit. For example, in synthesis “21.96g” should be 21.96 g. Make the corrections throughout the manuscript regarding values and units.
8) The author should provide reason about this statement “However, no results related to Ti is found in TEM characterization, which may be caused by the fact that CeO2 can inhibit the crystallization of other oxides during calcination process”.
9) Comparison of the present results with other similar findings in the literature should be discussed in more detail. This is necessary in order to place this work together with other work in the field and to give more credibility to the present results.
10) Conclusion part is very long. Make it brief and improve by adding the results of your studies.
11) There are many grammatic mistakes. Improve the English grammar of the manuscript.
Author Response
Dear Reviewer:
Thank you for your comments concerning our manuscript entitled “Enhanced catalytic performance of CeO2 supported TiO2-Pt nanorod in CO oxidation” (ID: molecules-2198344). Those comments are valuable and very helpful for revising and improving the manuscript, as well as the important guiding significance to our researches. According to the reviewers’ detailed suggestions, we have made a careful revision on the original manuscript. The revised are marked in yellow in the manuscript. The main corrections and the responds to the reviewers’ comments are as follows.
Response to reviewers’ comments:
Referee #3
Comment 1: In this manuscript, the authors did not explain the importance of the nanorod morphology in the introduction part. The authors should explain the importance of nanorod morphology.
Response: Thanks for reviewer’s kind suggestion very much. We have supplied the importance of the nanorod morphology in the introduction part. “Previous studies also imply that the morphology and facets of CeO2-based nanocomposites can greatly influence the formation and migration of surface oxygen vacancies, and nanosized structured CeO2 materials, including nanospheres, nanorods, nanocubes have been synthesized. Among these structures, nanorod-shaped CeO2 has received a substantial amount of attention because of its potentially large surface area and abundance of oxygen vacancy defects.”
Comment 2: Title: The title of the manuscript is not impressive. It should be modified or rewritten it.
Response: Thanks for reviewer’s suggestion. We have modified the title into “CeO2 supported TiO2-Pt nanorod composites as efficient catalyst for CO oxidation”.
Comment 3: Correct the following statement “The outstanding catalytic performance is ascribed to the stable structure and proper TiO2 doping as well as combined effect of Pt and TiO2. The research results are of importance for further development of high catalytic performance nanoporous catalytic materials”.
Response: Thanks for reviewer’s question. We have revised part of the content and think " The outstanding …combined effect of Pt, TiO2 and CeO2".
Comment 4: Keywords: There so many keywords and reduce them up to 5. So, modify the keywords.
Response: Thanks for reviewer’s question. The keywords in the manuscript is four, didn’t exceed 5. Thanks for your reminding!
Comment 5: Introduction part is not impressive. The references cited are very old. So, Improve it with some latest literature like 10.1016/j.chemosphere.2022.133772, 10.1016/j.eurpolymj.2021.110783
Response: Thanks for reviewer’s question. We have revised introduction part carefully. We mentioned the challenges of current catalytic materials and pointed the highlights or strong points of our current works. We have also referred the sate of art literatures in the manuscript, see ref. 4, 5.
Comment 6: The authors should explain the following statement with recent references, “The O 1s spectrum in Figure 2d can be fitted to three peaks”
Response: Thanks for reviewer’s question. The O 1s spectrum in Fig. 2d can be fitted to three peaks, and the corresponding binding energies are centered around ~529.3 eV, ~531 eV, ~ 532.2 eV, respectively. And the binding energies are corresponded to lattice oxygen species (Olat), surface adsorbed oxygen (Osur), weakly bonded specific oxygen species like adsorbed O2, H2O and CO2 (Obon), respectively.
Comment 7: Add space between magnitude and unit. For example, in synthesis “21.96g” should be 21.96 g. Make the corrections throughout the manuscript regarding values and units
Response: Thanks for reviewer’s question. We have checked and revised these mistakes and corrected them. We have also highlighted the wrong points.
Comment 8: The author should provide reason about this statement “However, no results related to Ti is found in TEM characterization, which may be caused by the fact that CeO2 can inhibit the crystallization of other oxides during calcination process”
Response: Thanks for reviewer’s question. No results related to Ti is found in TEM characterization, this may be because that the calcination temperature in (TiO2-Pt)/CeO2 system is relatively low (300 ℃); CeO2 can inhibit the crystallization of other oxides during calcination process under such low temperature [43]. Our previous work also found that CeO2 can inhibit the crystallization of NiO; as temperature raises, the structure of NiO in the system is transformed from amorphous state into crystallization state [36]. Therefore, the reason why the lattice fringe related to TiO2 is not detected in TEM characterization may be due to the amorphous state of TiO2 in the system, which is in line with XRD results.
Comment 9: Comparison of the present results with other similar findings in the literature should be discussed in more detail. This is necessary in order to place this work together with other work in the field and to give more credibility to the present results.
Response: Thanks for reviewer’s question. The catalytic activity of (0.5TiO2-Pt)/CeO2 also surpasses the state of art TiO2/CeO2-based catalysts reported in literature, as shown in Table S1, indicating its superior catalytic property.
Comment 10: Conclusion part is very long. Make it brief and improve by adding the results of your studies.
Response: Thanks for reviewer’s question. We have revised Conclusion part and added the results of studies.
Comment 11: There are many grammatic mistakes. Improve the English grammar of the manuscript.
Response: Thanks for reviewer’s question. We have checked the English grammar of the whole manuscript and revised the wrong parts. We have also polished the language of the whole manuscript and marked the revised places into yellow, please check, thanks!
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and frame work of the manuscript. And here we did not list the changes but marked in blue in the revised. We appreciate Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval. Once again, thank you very much for your comments and suggestions. Best wishes,
Sincerely yours!
Reviewer 4 Report
Molecules
Manuscript ID: molecules-2198344
Title: Enhanced catalytic performance of CeO2 supported TiO2-Pt nanorod in CO oxidation
In this manuscript, nanorod structured (TiO2-Pt)/CeO2 catalysts with addition of 0.3 at% Pt and different atomic ratio of Ti were prepared through a combined dealloying and calcination method. The catalysts were characterized by XRD, XPS, SEM, TEM and STEM in order to investigate the phase composition, surface morphology and structure of synthesized samples. I think that is an interesting experimental study, however, some issues should be improved. I recommend a publication of this work to Molecules journal after the authors consider the following major revisions.
Comment #1
The authors need to improve on their bibliography. I think that they should add some references in order to enrich the introduction section. In particular, the authors should improve the section of CeO2 in terms of the addition of other promoters into the structure, such as La3+, Sm3+ and or basic oxides in order to improve the physicochemical characteristics (basic sites, oxygen vacancies, oxygen mobility).
1. Y. Zhang, J. Xu, X. Xu, R. Xi, Y. Liu, X. Fang, X. Wang Tailoring La2Ce2O7 catalysts for low temperature oxidative coupling of methane by optimizing the preparation methods. Catal. Today, 355 (2020), pp. 518-528,
2. G.I. Siakavelas, N.D. Charisiou, A. AlKhoori, S. AlKhoori, V. Sebastian, S.J. Hinder, M.A. Baker, I.V. Yentekakis, K. Polychronopoulou, M.A. Goula, Highly selective and stable Ni/La-M (M=Sm, Pr, and Mg)-CeO2 catalysts for CO2 methanation. Journal of CO2 Utilization 51 (2021) 101618.
Comment #2
The authors need to be clearer on the motivation behind their work. Which is the innovation and what are the new aspects being introduced on this research topic? Please improve the introduction section
Comment #3
Which characterization technique the authors used for the measurement of Ni and promoters’ content?
Comment #4
The authors should correlate their catalytic performance results with the already published studies of different researchers to show the priority of their research study.
Comment #5
It possible for the authors to calculate kinetic data such as TOF or activation energy values?
Author Response
Dear Reviewer:
Thank you for your comments concerning our manuscript entitled “Enhanced catalytic performance of CeO2 supported TiO2-Pt nanorod in CO oxidation” (ID: molecules-2198344). Those comments are valuable and very helpful for revising and improving the manuscript, as well as the important guiding significance to our researches. According to the reviewers’ detailed suggestions, we have made a careful revision on the original manuscript. The revised are marked in yellow in the manuscript. The main corrections and the responds to the reviewers’ comments are as follows.
Response to reviewers’ comments:
Referee #4
Comment 1: The authors need to improve on their bibliography. I think that they should add some references in order to enrich the introduction section. In particular, the authors should improve the section of CeO2 in terms of the addition of other promoters into the structure, such as La3+, Sm3+ and or basic oxides in order to improve the physicochemical characteristics (basic sites, oxygen vacancies, oxygen mobility).
- Y. Zhang, J. Xu, X. Xu, R. Xi, Y. Liu, X. Fang, X. Wang Tailoring La2Ce2O7 catalysts for low temperature oxidative coupling of methane by optimizing the preparation methods. Catal. Today, 355 (2020), pp. 518-528,
- G.I. Siakavelas, N.D. Charisiou, A. AlKhoori, S. AlKhoori, V. Sebastian, S.J. Hinder, M.A. Baker, I.V. Yentekakis, K. Polychronopoulou, M.A. Goula, Highly selective and stable Ni/La-M (M=Sm, Pr, and Mg)-CeO2 catalysts for CO2 methanation. Journal of CO2 Utilization 51 (2021) 101618.
Response: Thanks for reviewer’s kind suggestion very much. We have revised introduction part carefully. We mentioned the challenges of current catalytic materials and pointed the highlights or strong points of our current works. We have also referred the sate of art literatures in the manuscript, see ref. 16, 17.
Comment 2: The authors need to be clearer on the motivation behind their work. Which is the innovation and what are the new aspects being introduced on this research topic? Please improve the introduction section
Response: Thanks for reviewer’s question. For one thing, Both theoretical and experimental studies have demonstrated that combing transition metal-oxides or rare with noble metals is an effective method to reduce cost while maintaining catalytic property stable, which has been widely used for fuel cell and energy conversion/storage equipment. For another, the conventional fabrication methods always require relative high cost, complicated or time-consuming preparation process, which limit their large-scale application. Herein, by rational adjusting the proportion of TiO2 in the system, the obtained (0.5TiO2-Pt)/CeO2 displays unique nanorod structure and large pore volume, which contributes to exceptional catalytic activity. We think this work provides a new idea for preparation of high catalytic performance transition metal/CeO2-based catalysts for large-scale production.
Comment 3: Which characterization technique the authors used for the measurement of Ni and promoters’ content.
Response: Thanks for reviewer’s question. The content of Al, Ce, Pt, Ti in (0.5TiO2-Pd)/CeO2 catalyst obtained from Al91.2Ce8Pt0.3Ti0.5 melt-spun ribbon is 3.81 at%, 90.14 at%, 1.66 at%, 4.4 at%, respectively, as shown from the EDS spectrum in Fig.S1.
Comment 4: The authors should correlate their catalytic performance results with the already published studies of different researchers to show the priority of their research study
Response: Thanks for reviewer’s question. The catalytic activity of (0.5TiO2-Pt)/CeO2 also surpasses the state of art TiO2/CeO2-based catalysts reported in literature, as shown in Table S1, indicating its superior catalytic property.
Comment 5: It possible for the authors to calculate kinetic data such as TOF or activation energy values
Response: Thanks for reviewer’s question. We have added the characterizations about the catalytic activity of (0.5TiO2-Pt)/CeO2 under different space velocities as well as the catalytic performance under varied oxygen concentrations, see Fig. 8. The catalytic performance of (0.5TiO2-Pt)/CeO2 as a function of flow rate at 70 °C is detected, with corresponding shown in Fig. 8a. As the total gas flow rate increases from 40 to 120 ml min-1, the CO conversion decreases from 97% to 58%. It can be also clearly detected that the reaction rate is positive related to flow rate. Fig. 8b further explores the influence of O2 concentration in feed gas on catalytic performance of (0.5TiO2-Pt)/CeO2. The test temperature is kept at 90 °C with flow rate100 mL min-1. The CO conversion rate can reach 99% as 10% O2 is initially infused into the system thanks to the sufficient O2 environment; CO conversion rate is reduced first and then kept stable at 10% when O2 supply is suddenly decreased to zero, which may be ascribed to the existence of surface lattice oxygen that can migrate to active sites and combine with adsorbed CO to form oxygen vacancies. However, CO conversion rate increases in poor oxygen condition (0.3-5% O2) and then recovers to initial 99% value and keeps unchanged when O2 is resupplied into feed gas, implying superior catalytic CO oxidation property of (0.5TiO2-Pt)/CeO2.
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and frame work of the manuscript. And here we did not list the changes but marked in blue in the revised. We appreciate Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval. Once again, thank you very much for your comments and suggestions. Best wishes,
Sincerely yours!
Round 2
Reviewer 1 Report
Dear Editor
The paper was revised according to the reviewer’ comments.
In its current state it is ready for publication in your journal.
Best regards
Reviewer 2 Report
accept
Reviewer 4 Report
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