Glycine–Nitrate Combustion Synthesis of Cu-Based Nanoparticles for NP9EO Degradation Applications
Round 1
Reviewer 1 Report
This manuscript reports the synthesis of Cu based-nanoparticles by glycine–nitrate process (GNP). The morphological and composition characterization of the nanoparticles was evaluated by SEM, XPS, DRX, and BET. The materials were tested as photocatalysts for the degradation of nonylphenol-9-polyethoxylate (NP9EO).
Although the authors have done good work, the following points need to be carefully addressed:
- The absorption spectra of the materials should be presented.
- A brief description of the appearance (color) of the powders should be presented.
- Because of the band gap of the Cu2O and CuO are 2 eV and 1.6 eV, respectively, these semiconductors are attractive for photocatalytic reaction under visible light. What is the purpose of reporting the activity only under UV light? It would be very interesting to report also the activity of the materials under visible light.
- In the 322-line, the author suggests that the integration of Cu2O and CuO significantly increased charge collection and reduce the recombination. The author could also referee to https://doi.org/10.1016/j.apcata.2015.10.044 to provide more support to the statement.
- The last paragraph (329-334 lines) in the results and discussion section is not clear.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Authors have shown that they have taken x ray structure of synthesized cu Nano particle. They have not shown the data. It will be nice if they will put that data in the paper as well.
Author Response
請參閱附件。
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors had responded my comments in a good way, and this revised manuscript can be accepted as it is.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
The manuscript describe the synthesis and use of a copper oxide catalyst. While the procedure and the results look interesting some issues should be addressed before I can accept it for publication.
- Please revise the writing of the introduction, sometimes is confusing.
- Line 66: Remove the parenthesis, it is repetitive.
- Line 75-78: Please add a reference to that sentence.
- Line 103: Why do you add a reference there if that is the result of your work? This happen along the manuscript, it is not clear sometimes what is a result and what is a previous work.
- Figure 2: Those images show a lot of polidispersity and aggregation. Can you provide images of the countour lines provided by imageJ program?
- Figure 3: Are the TEM and SEM images from the same samples? It certainly doesn't look so...
- Figure 4: The XPS is confusing. b), c) and d) are the real signal or the deconvolution of the signal?. In any case, you should show a real amplification of the part of the graph from where that graphs come from.
- Section 2.2: The irradiation system should be described here.
- The authors should describe clearly how they measured the NP9EO removal and how they calculated the TOC.
- 295-296: Please explain that last sentence, it is very confusing.
- I really don't think the final ANOVA analysis add anything to this work. You could just mention the result of it along the manuscript.
- Figures 7, 8 and 9 should be within the main text not in the Materials and Methds section.
- Conclusions look like another abstract. Please re-write it.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
The introduction of the article provides insufficient background and is presented as random, mixed ideas. For instance, the authors mentioned the importance of minimizing the amount of noble metals in the design of a catalyst without affecting their performance in the photoreforming process. However, the paper focuses neither on the H2 evolution nor bimetallic particles. Then, it is pointless to provide such information.
The article focuses on the study of Cu-based photocatalysts for organic degradation. Cu2O-CuO, CuO-Cu2O-Cu, and Cu2O-Cu are the materials evaluated in this paper. There is vast information about copper oxides as photocatalysts that should be mentioned in the introduction. For instance, it has been reported that Cu2O-CuO influences the dynamic of charge carriers improving its photocatalytic activity. Also, it should be mentioned the motivation to decompose NP9EO, since it is not a compound commonly used to evaluate the photoactivity of a material.
The research design needs to be improved. The adsorption of NP9EO before illumination is missing. Profiles of degradation and TOC should be presented for a better understanding. The absorption spectrum of the samples is fundamental in a photocatalytic study. Bare CuO and Cu2O should also be evaluated as reference. The sample G/N=0.7 is the second more active photocatalysts, even though it contains only a small amount of Cu2O (semiconductor). Is this correct? Because it is unexpected from the photocatalytic point of view.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I really appreciate the effort shown by the authors in the revision of the manuscript but I am still not convinced in some aspects.
- About Fig 2. In the manuscript the authors say, “TEM size analysis was performed using Image J software using a macro to outline the edges of particles and determine their diameter”. Since the images provided show aggregated particles I asked the authors to provide the edges outlined by the program in order to determine their sizes because I find it very difficult to believe anyone can obtain reliable values from those images (and even more difficult to believe the standard deviations provided….). Also, there is a square drawn in every image (not described in the caption…) with the same scale bar as the whole image, what is it?
- Figure 3. I still don’t see the similarity between figures 2 and 3. I understand that TEM and SEM images are not the same but they should show similar features when using the same scale. By the way, it would be very helpful to add scale bars to the SEM images.
- About XPS, figure 4. Are the authors saying that figures 4b-4d are real signals obtained? I’m sorry but I just can’t believe that you obtained that from a direct measurement of your samples. If it is a deconvolution of the signal you should explain that on the manuscript and in the caption.
- Line 318-320. The authors say, “Cu2O (bandgap of approximately 2.2 eV) has higher electric conductivity than CuO (bandgap of approximately 1.6 eV) [39]; therefore, Cu2O exhibits a higher removal effect than CuO in a photocatalytic system”. Since when a higher bandgap means a better performance as a photocatalyst? The explanation about the activity of the catalyst is simply wrong. There is many factor that could affect the photocatalytic behavior. Also, an absorption spectrum of each catalyst would be very helpful in this case.
For these reasons I can't recommend the acceptance of this manuscript to be published.
Author Response
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Author Response File: 
Author Response.doc
Reviewer 2 Report
The authors have improved the motivation of the work and result presentations, remarkably. This paper can be accepted as it is.
Author Response
Please see the attachment.
Author Response File: Author Response.doc
Round 3
Reviewer 1 Report
Since the authors didn’t answer properly I’m afraid I have to reject this manuscript for publication in Catalyst. I would like to add some comments on the authors response:
- About ImageJ: The authors provide a table from the program where the size can be obtained but didn’t show any image where they can confirm the lines the program draw are correct (and thus the size they provide….). Using that program I found many times mistakes in taking sizes from the automatic drawing so visual revision of the output is mandatory to confirm the the drawing is ok, with more reason in aggregated samples.
- The authors comment that since the TEM images are not reliable and since “the information the TEM images provide only focused on the nanoparticle size, which, if deleted, would not affect the understanding of the whole article”. Size of nanoparticles in catalysis is an important issue if you want to compare different materials…
- About the photocatalytic activity, I am a photochemist with several years experience in light interaction with matter so I’m fully aware of what a bandgap is and its relationship with light absorption. Still, it doesn’t justify at all a better performance of a photocatalyst having a lower or higher bandgap. There are many other things that will influence a material photocatalytic activity way more than its bandgap. Also, since the journal is Catalyst, and you are synthesizing a photocatalyst, the absorption spectrum of the material is important and explaining the mechanism even more.
