Preparation of CeO2/UiO-66-NH2 Heterojunction and Study on a Photocatalytic Degradation Mechanism
Round 1
Reviewer 1 Report
Dear Authors
Thank you for your request for reviewing the manuscript.
Please, find my scientific opinion on the manuscript.
Authors should be improving some Characterization and add some more other as TEM, BET and XPS.
Sincerely yours,
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Reviewer 2 Report
In this paper, the authors report the preparing of MOF and CeO2 composite by hydrothermal methods. The MOF is prepared in this work is related to UiO-66-NH2. The resulting materials are applied in the degradation of rhodamine B by photocatalysis. The authors claim on obtaining synergistic effect by the combination between CeO2 and UiO-66-NH2 in the photocatalytic reactions and they attribute this to heterojunction structure. The authors indicated that TEM analysis indicated the formation heterojunction structure (Figure 10d), but the TEM image does not support this, and EDX mapping should be added to approve this result. Also, the authors assume the enhancement in photocatalytic performance is due this heterojunction structure, and here the authors should add more control experiments to prove that. For example, they should try to create a buffer layer, such a hydrophobic layer, between the CeO2 surface and the UiO-66-NH2. Over the whole text there is improper usage of phrases or unclear sentences that should be corrected.
For example:
Abstract: “The properties on photocatalytic aspects”; “SEM consequences states”; “which is much taller”; “for the same situations”; “to the partion of photocarriers”; “major the
liveness of substances”
Page 2: “1.39g Ce(NO3)3•6H2O and 0.75g NH4HCO3 were dissolved in 200mL deionized water, respectively”; “kettle lined with ptfe”
Page 3: “centrifuged for washing”; “the The scope of variation”
Page 4: “With the growth of temperature”; “match accord with”; “indicating the tall purity”; “can be distributed to the (111)”;
Page 5: “The consequences are described in Figure 6”; “sheets gradually increases with the temperature rises”
Page 6: “decreases with the content of UiO-66-NH2 reduce”; “which will be studied in the future photocatalytic test”
Page 7: “octahedral construction with a longest length”; “These consequences indicate”
Page 8: “with previous literatures”;
Page 9: “are counted to be”; “CeO2 and unoccuated molecular”
Page 10: “1.91 eV, sequentially”; “photocatalytic liveness”; “the arc is correlationed to”; “the consequences of EIS”; “Generally speaking,”
Page 11: “photocatalytic liveness”; “he catalyst in simulated wastewater is 10mg”; “tendency of first rising and then falling”; “porous constitute”; “The tall degradation efficiency”; “has finely oxidation power.”; “the two catalysts are compounded”; “it generate a decline in the reaction speed, which may be because”; “or may be transformed to”
Page 12: “adding the appropriate quality of UiO-66-NH2”; “C0 is the origina concentration”; “When CeO2 temperature is too high and the composite amount is too much,”; “liveness of substances involved”; “potential machine made”; “And then dot OH. •OH plays”;
Page 14: “It observed that”; “liveness of substances “
In addition, Figure 2 does not represent exactly the process described in the text as the CeO2 was added to the solution of the MOF components. Figure 11-14 are not of high quality and this should be improved. In page 12, “IPA”, “BQ”, “Na2C2O4” should be defined. Finally, the authors should add measurements of surface area.
Author Response
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Reviewer 3 Report
Cerium oxide is an efficient catalyst in various applications. The different ways to improve its catalytic activity, like stoichiometry variation, doping with different substances, et al. The present work explores an interesting approach when in two-dimensional sheet of CeO2 the UiO-66-NH2 nanoparticles are embedded by hydro-thermal method. This photocatalyst structure demonstrates better degradation efficiency compared to CeO2 and UiO-66-NH2 on their own. It is demonstrated that this is due to a certain morphology of heterostructure that provides a large contact area for the charge transfer. The strength of the work: Combination of precise sample preparation techniques and complementary characterization tools enabling quite convincing results. Quite high application relevance of the work. The weakness: Keeping in mind the reducible character of ceria, the work would gain if to follow how the ionic state of Ce changes during photocatalytic performance/degradation, for instance by XPS. In general, the work is scientifically sound, logically arranged and clearly presented. Reference list is comprehensive and up-to-dated. In my view, the manuscript is suitable for publication in Materials in its present form. The only technical suggestion is to improve the quality of Figure 13. Also, the style of sentence “Through the free radical capture experiment, it can be inferred that the major the liveness of substances involved in the degradation related to photocatalysis is H+ and ∙?2−.” needs revision for clarity.Author Response
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Reviewer 4 Report
Review of the Manuscript materials-1622372
- English text should be improved, and the Abstract, Introduction, Results and Conclusions should be rewritten
Abstract.
“The properties on photocatalytic aspects and degradation mechanism of Ce/UN were researched carefully. SEM consequences states that Ce/UN have a 3D flower-like structure, in which octahedral UiO-66-NH2 nanoparticles are embedded in the two-dimensional sheet of CeO2. TEM consequences states that CeO2 and UiO-66-NH2 interfacial link to constitute a heterojunction construction. Electrochemical impedance spectroscopy and fluorescence spectrophotometer conse-quences states that Ce/UN has less charge shift resistance and luminescence intensity contrasted with two pure substances. When the quality proportion of Ce/UN is 1:1 and the calcination temperature of CeO2 in Ce/UN is 400℃, the degradation efficiency of RhB in photocatalysis by Ce/UN is roughly 96%, which is much taller than CeO2 (4.5%) and UiO-66-NH2 (54%) for the same situations. The enhancement of the properties in photocatalysis of the Ce/UN may be because of the construction of heterojunction, which is conducive to the partion of photocarriers and the interfacial charge shift efficiency enchanced. By the free radical capture testment, it can be inferred that the major the liveness of substances involved in the degradation related to photocatalysis is H+ and ∙?2−.”
Should be replaced by
“The properties, photocatalytic aspects and degradation mechanism of Ce/UN were studied carefully. SEM results show that Ce/UN have a 3D flower-like structure, where octahedral UiO-66-NH2 nanoparticles are embedded in the two-dimensional sheet of CeO2. TEM results demonstrate that CeO2 and UiO-66-NH2 are bonded interfacially to constitute a hetero-junction construction. Data obtained by electrochemical impedance spectroscopy and fluorescence spectroscopy established that Ce/UN has less charge shift resistance and luminescence intensity than these of two pure substances. When the ratio of Ce/UN is 1:1, and the calcination temperature 400℃ is used, the degradation efficiency of RhB in photocatalysis by obtained Ce/UN is about 96%, which is much higher than in the case of CeO2 (4.5%) and UiO-66-NH2 (54%). The improved photocatalytic properties of Ce/UN may be due to formation of hetero-junction, which is conducive for most photo-carriers and thus the interfacial charge shift efficiency is enchanced. By the free radical capture test, it can be inferred that the major the active substances involved in the degradation related to photocatalysis is H+ and ∙?2−.”
- Introduction
“Accompanied by the fast evolution of industry, renewable sources and environmental problems have caused much attention [1-4].”
Should be substituted with
“Fast industry development in the last decades leads to increased environmental pollution, which have to be solved, whereas renewable sources and environmental problems have caused much attention by the researchers [1-4].“
- Authors should add results for BET and pores size distribution if available.
- Please correct the references according to journal requirements.
Author Response
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Round 2
Reviewer 2 Report
The revised paper has been significantly improved.
There still some minor corrections in English are required:
for example:
line 11: "Marked" should be "marked"
line 30: "which have to be solved" should be "which has to be solved"
line 94: "reaction teflon lining" is not clear what the authors want to describe. Do they mean " teflon lined hydrothermal autoclave"?
line 95: " then centrifugal washing" still not clear what they want to describe here
line 137: "EIS was tested in the range is from" should be "EIS was tested in the range of"
line 160: "are distributed on the (111)" should be "are related to (111)"
line 193: "photocatalytic experiments section" should be "photocatalytic experimental section"
line 247: "specifific" should be "specific"
line 253: "classifification" should be "classification"
line 254: "confifirmed" should be "confirmed"
line 258: " had mesoporous" should be "has mesopores"
line 258" specifc" should be "specific"
line 259: "As shown" should be "as shown"
line 294: "unoccuated" should be "unoccupied"
line 388: "Isopropyl " should be "isopropyl"
line 389: "p-Benzoquinone" should be "p-benzoquinone"
lines 397-398: "that H+ and ∙ ?2 are the main factors to degradation of RhB. And then •OH" should be" that H+ and ∙ O2 are the main species responsible for the degradation of RhB rather than •OH."
line 404: "As shown" should be "as shown)
line 433: "substances" should be "species"
Author Response
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Reviewer 4 Report
Accept in present form
Author Response
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