In Situ Synthesis of CuO/Cu2O Nanoparticle-Coating Nanoporous Alumina Membranes with Photocatalytic Activity under Visible Light Radiation
Round 1
Reviewer 1 Report
The authors report the synthesis and characterization of CuO/Cu2O film supported on nanoporous alumina membranes and the photocatalytic properties in the removal of MO. However, there are many problems need to be addressed. I suggest that the article be reconsidered after major revision.
1. The contents in Table 1 are unimportant and unnecessary, either in supporting information or summarized in text form.
2. It is better to compare the data of the three figures in Figure 3 in one figure, and mark the corresponding wave number of important peaks.
3. Figure 4 is not standard. Except for X and Y axes, the scale lines of other axes should not appear.
4. No corresponding a,b and c can be seen in Figure 5.
5. Figure 7 clearly has four figures, but only see the three legend of (a,b,c).
6. In Figure 7b, it can be seen that there was a great decrease in MO concentration under dark conditions, and the decrease trend was close to that under light conditions, and there was no significant difference in catalytic activity between the two. Therefore, the photocatalytic performance of the catalyst is doubtful, and it is more likely to be due to the adsorption of porous materials. More proof experiments need to be carried out.
7. MO has a photosensitive effect, and its concentration change cannot be used to evaluate the photocatalytic degradation activity alone. Colorless organic matter is also needed to evaluate the activity of the catalyst. The author should degrade some colorless organic matter or antibiotics to enhance the argument. You can refer to “Chemical Engineering Journal, 2021, 411, 128615.”, “Applied Surface Science, 2018, 427, 1046-1053” and “Water 2021, 13, 288”. In addition, the cyclic degradation experiment is still necessary.
8. As your said, “the copper(I and II) oxide nanoparticles on the Al2O3 membranes play a pivotal role in the photocatalytic process of MO degradation”, This mechanism should be illustrated in Figure 7c.
9. There are too many spelling and typographical errors, such as "Somerecent reports" without Spaces, "1200cd-1could" without Spaces, "HClO4" without subscripts, "Figure 7C" should be lowercase "c", and so on.
Author Response
Thank you for your comments and contributions to improve the manuscript. The answers to each of the points is in the attached file.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article describes in sufficient detail the method of preparation of Cu-containing films supported on nanoporous alumina membranes and their study by FTIR and UV-visible spectroscopy, XPS ,SEM, EDS.
Finally, it was prepared well-ordered nanostructured coating.
From this point of view, the content of the article corresponds to the field of the journal Coatings.
However, the main criticism is that the obtained samples exhibit too little photocatalytic activity in the degradation of MO. A decrease in the MO content in the solution is associated with adsorption. Light irradiation reduces concentration of MO only by 20% during 2 hours. Such small activity does not allow consider the material as a promising photocatalyst. Usually materials demonstrate much more activity as in references [17-19].
Some comments.
1. What data allow conclude that there are coper oxides in samples? Data of XRD analysis should be present.
2. There is not any information about the content of coper in samples.
3. Fig.7c is too general scheme for semiconductor. It does not consist with presence of two oxides and with “heterojunction” mentioned by authors.
4. There is a big difference in the quality and the style of the drawings of figures. Fig.3 is rather blind drawing.
5. There are confusing with number of Figures (line 311).
6. English (spelling) should be checked along the text (e.g. Line 18).
Author Response
Thank you for your comments and contributions to improve the manuscript. The answers to each of the points is in the attached file.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have solved most of the problems, but there are still a few minor issues that need to be corrected. It can be accepted after minor revisions.
1. In the revised PDF, some figures are garbled. I'm not sure the authors ever revised it. Such as Figures 3, 4b, 7d.
2. As your response, “control experiments were carried out where MO was subjected to the same conditions in the absence of a membrane and in the presence of the membrane prior to the incorporation of CuO/CU2O, using light radiation.” and “the recycling experiments were carried out up to three cycles.” However, Specific experimental results were not shown in the revised version.
Author Response
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Author Response File: Author Response.docx
Reviewer 2 Report
The paper could be accepted after at least following corrections.
1. The last part of Fig.7 - d) Illustration of the reaction mechanism for MO degradation under light irradiation conditions - should be exсlude. The same from the text.
2. In conclusions to change the end.
Last sentences could be only " The in-situ formation of copper oxide nanoparticles in the anodic alumina membranes generated significant changes in the chemical, optical, morphological, and photocatalytic properties in MO photodegradation".
With such corrections there is only testing of the photocatalytic activity.
For well-done work for the preparatiom of the coating it will be enough.
Author Response
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Author Response File: Author Response.docx
