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  • Diego Alvarez-Bustos 1,
  • Felipe Sanchez-Minero 1 and
  • Carlos Eduardo Santolalla-Vargas 2,*
  • et al.

Reviewer 1: Anonymous Reviewer 2: Anonymous Reviewer 3: Anonymous

Round 1

Reviewer 1 Report

In the paper entitled „Synthesis and Evaluation of FeSX/TiO2 for the Photocatalytic Degradation of Phenol under visible light region”, Alvarez and co-workers presented studies of the new type of chemically modified material based on titania impregnated with iron sulphide and chloride for  photodegradation of common water pollutants. The obtained heterogeneous catalysts were characterized with the use of Raman and XPS spectrometry. The results of photodegradation of phenol seem to be interesting and worth publishing in Catalysts. However, the major revision needs to be performed. There are some issues that should be corrected/explained/investigated:


1. In the Introduction section the Authors claimed that the band gap energies are decreased when the iron and chloride doping of TiO2 occur. However, the obtained values of the band gap energies presented in Table 1 are not entirely consistent with this statement. The energy is significantly increased in Fe-Cl in comparison to Fe-0.5Cl. If the measurements were correctly performed, they should be clearly explained and discussed with literature data. The same phenomenon was observed in the case of FeS catalysts (Table 4).


2. The photocatalytic activity plots of both oxide and sulphide catalysts demonstrated nonlinear phenol degradation. The Authors should try to explain this fact. Also, the degradation rates (Δc/t and R2) should be calculated.

3. The characterization of catalysts needs to be supplemented with SEM images. If it’s not possible, at least particle size and distribution should be measured by DLS.

4. The methodology of photocatalytic reactions is insufficient described. What was the exact wavelength of the LED lamp? Was it white light or other?
5. The DRS UV-Vis spectra showed the highest absorbance at approx. 350 nm in the case of every catalyst. In my opinion, the photocatalytic degradation should be also performed with the use of UV light to use the synergic effect of TiO2 and Fe.

6. The spectra presented in Figure 2 are mirror images. Please correct

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript (Manuscript ID catalysts-1636999) reports the synthesis and study of FeSX/TiO2 for their use as photocatalyst in phenol degradation. This manuscript presents timely research and is aligned with the scope of the journal. However, the materials synthesized and used have not been described or detailed in the materials and methods section, being this essential to understand and reproduced the results showed. Also, the Hydra program should be described in more detail.  For this reason, this work may not be published in Catalyst in its present form. Only after major changes, may result in a more solid work which could be considered again. The authors are asked to modify their manuscript according to the following specific points in order to come up with a revised version of their work.

The following issues should be addressed:

  1. The synthesis of materials and characterization techniques (XPS and TPR) used in this work should described in deeper in materials and methods section.
  2. The Hydra program should be described in more detail and give  adequates reference to explain these diagrams in catalysis area. Also, might be interesting show how was calculated the chemical equilibrium diagram.
  3. The authors need to provide more novelty in this work, since the study of photocatalysis in Phenol degradation has been widely studied. Moreover, there are several works that present better results in phenol conversion, such as S.Chatterjee et al. J. Photochem. Photobiol. A: Chem, 81(1994) 199, W. Wang et al. J. Mol. Cat. A: Chem. 235 (2005)194, J. Wang et al. Mat. Lett. 179 (2016) 42. However, currently this topic is interesting for the scientific community.
  4. The authors should explain how they performed the UV-Vis spectrum, since in the range 300-400 nm there are a lot of noise or severals peaks.
  5. Why did the authors use for oxide catalyst one techniques (UV-Vis and TPR analysis) and for sulphated catalyst another (XPS and Raman)?
  6. In XPS analyses, the deconvolution of all the peaks should be showed with the aim of understand the values of table 5.
  7. There is a discrepancy between the values of degradation and the TOC values. Can this reaction generate sub-products?
  8. Did the authors study the samplesstability in the photocatalytic reactions?
  9. In the section Discussion (Linea 324) the authors comment the -OH groups of the titania. However, they did not analyze the chemistry surface of the TiO2.
  10. A better description of Figure 21 might be performed. Since the authors might interprete the oxidant species generated in the catalyst and why one catalyst can be more interesting that another in this reaction. In this sense the use of scavenger can be interesting to understand the mechanism of the reaction of these catalysts.
  11. I can not see the Figure 1 and 2 adequately.
  12. The language of the manuscript should be checked carefully as there are many typos and grammar mistakes. These should be corrected before resubmission. For example, line 173 Tio2.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Santolalla-Vargas and coworkers demonstrated an interesting work using TiO2 impregnated with iron sulphide and chlorine heterostructures for the photocatalytic reaction of degradation of phenol. However, the figures and writing could be improved, and some control experiments are missing. The following questions must be addressed before publication.
1. Figures quality is quite low. For example, Figures 1-4, Figure 6, Figure 8 and others. More specific points the authors should address (1) Some figures look like a photo of the raw data. Figure 3 and Figure 9 as examples. If so, the authors should plot them. (2). Figures 1-2 look like a mirror image and must be corrected. (3). The color of the lines is hard to tell the difference. Examples include Figures 6-8 (4). The axis is messy. Figure 10 is an example. (5). If one figure contains a couple of small figures, please add sub-notes such as (a)(b)(c)(d) to them.
2. Typos. There are a couple of typos and grammar mistakes in the text. Please correct them. Some example, on page 2, Fe2O3, “2” and “3” should be subscript. A lot of similar typos could be found in the paper.
3. The light wavelength of the light sources is missing.
4. Could you give the detailed methods to obtain phenol concentration in the methods section? The authors mentioned Shimadzu TOC-Lcph/n total organic carbon (TOC) instrument. Is this instrument usually for phenol concentration? I usually see researchers use HPLC or NMR.
5.  The introduction of photocatalysis could be expanded and more papers could be cited. Some introduction of the advantages of the heterostructures photocatalysts (could also be called composites photocatalysts as the authors used in their study) over the pristine one should be added in the main text and some recent paper about heterostructures photocatalysis could be cited (https://doi.org/10.1021/acsmaterialslett.1c00785; https://pubs.rsc.org/en/content/articlelanding/2021/ta/d1ta07733c).
6. What is the experiment that the “phololyst” in Figure 13 stands for? The authors must note it in the main text.
7. The control experiment with photocatalyst but in the dark is missing and should be added.
8. Could you draw the mechanism of the degradation of phenol. What are the products?
9. The references format has a lot of problems. Some examples such as ref 19, 24 and others. The authors should not use et.al but show all the authors' names.
10. Is figure 21 obtained from the author's xps data or reference 41? The authors should be more clear about it. Also, the redox potential of phenol could be measured and added in the figure, if the reaction mechanism is the direct reduction of phenol.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors,

Thank you very much for your reply. I have no further comments. The paper can be published in Catalysts.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript (Manuscript ID catalysts-1636999) reports the synthesis and study of FeSX/TiO2 for their use as photocatalyst in phenol degradation. The authors carefully addressed all the comment asked in the previous revision. However, this article still presents several lacks that the authors should be resolved before its publication in Catalyst.

The following issues should be addressed:

  1. The authors should describe better the novelty of the paper in the last introduction paragraph.
  2. The authors should describe in more depth the UV-Vis spectrum of the samples, since in the range 300-400 nm there are a lot of noise or several peaks. The DRS UV-Vis are difficult to understand since this material does not absorb at 200 nm and usually the TiO2 absorb in this range.
  3. The band gap of the samples should be check due there are two slopes in the spectrum, see Figure 4. B. The authors might follow this ref (J. Phys. Chem. Lett. 2018, 9, 6814−6817) to do the analysis.
  4. The band gap of your samples is around 3 eV, being this band gap so high for the absorption in visible light. Why these catalysts are active in visible light (LEDs of 450 nm and 550 nm)? The samples should not be active in visible range if you observe the band gap of the samples
  5. A study or description of the sub-product should be described in the manuscript since this sub-product can be more dangerous than the phenol.
  6. The interpretation of Figure 21 is difficult, since your material is a ternary system (FeO-FeS/TiO2) and the interpretation of this heteroconjunction (II heteroconjuntion, Z-schemes) is so difficult. For this interpretation you need the use of scavenger, PL …
  7. The authors should describe the titania used for this work
  8. The language of the manuscript should be checked carefully as there are many typos and grammar mistakes.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The revised version looks good, and the authors revised the paper with care. This paper should be published in current form. Just one minor comments, the authors could double check the format of the references, as some of them do not look the same format. For example, some references show the full name of the authors' list but some did not. But I think this can be checked by the English correction process via the journal.

Author Response

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Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

The manuscript (Manuscript ID catalysts-1636999) reports the synthesis and study of FeSX/TiO2 for their use as photocatalyst in phenol degradation. The authors carefully addressed all the comment asked in the previous revision This paper is adequated to publish in Catalyst. However I would like to mention two comments without so relevance:

1) The authors should incorporated in the manuscript the characteristic or properties of the commercial TiO2.

2)The authors should incorporated in thte manuscript that in thsi work the do not study the sub-products of the phenol degration.