Hydrogen Production and Degradation of Ciprofloxacin by Ag@TiO₂-MoS₂ Photocatalysts

Round 1

Reviewer 1 Report

The authors report on the synthesis of silver and molybdenum disulfide photocatalysts for the production of hydrogen and degradation of ciprofloxacin, and the materials were characterized by several methods. Overall, the work is well-aimed and reports interesting data on the preparation of efficient catalyst for degradation of ciprofloxacin. However, the following points should be carefully considered and accordingly revised:

• Manuscript neededto be technically edited because some sections were abbreviated and were not explained enough. Line 27: the meaning of "NWs" was not clearly stated.
• Define the abbreviations which were first used in the abstract and redefinedthem when they first appeared in the main text of the manuscript. In lines 31-32: "FE-SEM... XPS" appeared for the first time in the abstract of the manuscript, the full name of them should be written, and the full name should also be indicated when it appeared for the first time in the main
• All Figures appearing in the manuscript shouldbe modified according to relevant format requirements, and all Figures should be immediately followed by Figure legend (The words which were describe from Line 186 to Line 190 should be moved to Line 194), and the description of the main text should not be interspersed between the Figure and Figure legend. Such problems existed in Figure 1, Figure 2, Figure 4 and Figure 5 in the manuscript. Above problems should be revised.
• Lines 123-128: only the HRTEM stripes of Ag element wereprovided in Figure 3. At the same time, the author should also provide the stripe images of TiO₂ and MoS₂, provide the selected area diffraction spot pattern of the composite catalyst in the experiment, and mark the indices of crystallographic plane of each light
• Line (c) in Figure 4 also neededto provide a fitting curve, even if it did not coincide with other peaks.
• The Figures in the main text should be standardized. In Figures 5, 6, 7, 8 and 9, the horizontal coordinateand vertical coordinate inside every Figure should be deleted and the coordinates should be placed on the outside. And please use the same Figure size and presentation mode for all Figures which were presented in the manuscript.
• In addition to above problems, the meaningof a, b, c, d, e or f was not clearly shown within Figure 5. It could be considered to show the meaning of a, b, c, d, e or f within Figure  The authors could redraw the XRD pattern of a, b, c, d, e or f into a single Figure, or the authors could divide Figure 5 into two Figures which were marked with (a) and (b). In addition, the unit of the y ordinate in Figure 5 should be changed to (a.u.), and the peak which was represented by "* - Ag NPs" whith tFigure 5 on the left side was not seen clearly, as a result, the existence of Ag could be proved by using Figure 5. Please modify it. We could not find the diffraction peaks of "A-anatase"on the right side of Figure 5. "A-anatase" could be deleted from the right side of Figure 5. 
• (a) and (b)were not mentioned in the legend of Figure 6. We could not distinguish (a), (b), a and b within Figure 6, please make appropriate modifications.
• In Figure 7, in addition to above problems, it should also be noted that the y ordinate of Figure 7 should contain“Removal rate of degrading ciprofloxacin (%)" in stead of “% degradation”.  
• Based on the experimental data in Fig. 7, the authorsshould also provide the adsorption removal rate for a certain period of time under dark conditions. At the same time, the data spectrum of direct photolysis without catalyst should be
• The first half of the manuscript didnot explain whether light was needed during the experiment. And it is not specified whether to use visible light or ultraviolet light. Please specify the specific light irradiation conditions for the experiment in the main text and Figure legend.
• The y ordinate in Figure 8 was described by"A / A₀". Please explain the meaning of "A / A₀". If the authors want to express the ratio of concentration to initial concentration, "C / C₀" could be used.
• It couldbe seen from Figure 11 that H₂ was finally generated. The authors should provide the methods for calculating the relevant illumination intensity. The author should calculate the light quantum efficiency and the value of "turn over" for producing H₂.
• Author should completely check and revise the format of their manuscript according to the author guidelines of the For example, the format of “2.1.1. FE-SEM and EDS” should be the same as the format of “2.1.2. HRTEM” or “2.1.3. BET analysis” or “2.1.4. XPS analysis”, as a result, there was not 4 spacing before “2.1.1. FE-SEM and EDS” or “2.1.2. HRTEM” or “2.1.3. BET analysis” or “2.1.4. XPS analysis” or “2.1.5. XRD analysis” or “2.1.6. Raman analysis ”. Please make corresponding adjustments.
• Please explain the number "276" in Table 3.
• "2.1.6" appearedtwice in line 195 and line 212 of the manuscript. Please explain the reason or modify it.
• The initials of "analysis" which appearedin “1.3. BET analysis” or “2.1.4. XPS analysis” or “2.1.5. XRD analysis” or “2.1.6. Raman analysis ” should be capitalized. Note that the format which appeared before the manuscript and after the manuscript should be unified.
• In line 414, "25oC" appeared. Please explain the meaning of "oC" which was different from "℃" which appeared in line 426. Did the author create a new symbol? Please explain it.
• Please provide the possible degradation path of the pollutant during the experiment. Please providethe intermediate products during the degradation process of ciprofloxacin.
• Please provide the relevant UV-Vis diffuse reflectance absorption spectra of the catalysts. Please providethe energy band width of each catalyst which was involved in the article.
• Please provide error bars for all degradation curves which were contained in the manuscript.
• In addition, a polishing of the English grammarwould be required in order to improve the readability of the manuscript.

Comments for author File: Comments.pdf

Author Response

Response to the comments of reviewers and list of changes introduced in the revised version

Reviewer #1:

• Manuscript needed to be technically edited because some sections were abbreviated and were not explained enough. Line 27: the meaning of "NWs" was not clearly stated.

The reviewer is absolutely right. The manuscript has been amended to clarify the different acronyms used in the text.

• Define the abbreviations which were first used in the abstract and redefined them when they first appeared in the main text of the manuscript. In lines 31-32: "FE-SEM... XPS" appeared for the first time in the abstract of the manuscript, the full name of them should be written, and the full name should also be indicated when it appeared for the first time in the main.

The manuscript has been modified as indicated by the reviewer.

• All Figures appearing in the manuscript should be modified according to relevant format requirements, and all Figures should be immediately followed by Figure legend (The words which were describe from Line 186 to Line 190 should be moved to Line 194), and the description of the main text should not be interspersed between the Figure and Figure legend. Such problems existed in Figure 1, Figure 2, Figure 4 and Figure 5 in the manuscript. Above problems should be revised.

The reviewer is right. There was a problem with the format and position of some of the figures and their corresponding captions. This problem has been completely corrected in the revised version of the manuscript.

• Lines 123-128: only the HRTEM stripes of Ag element were provided in Figure 3. At the same time, the author should also provide the stripe images of TiO2 and MoS2, provide the selected area diffraction spot pattern of the composite catalyst in the experiment, and mark the indices of crystallographic plane of each light.

The changes suggested by the reviewer have been considered and Figure 3 has been modified to include the lattice spacing of TiO₂ (110) and MoS₂ (100). For these figures, and due to a technical problem when they were being recorded, it was not possible to obtain the electron diffraction pattern (SAED), so this information has not been included.

• Line (c) in Figure 4 also needed to provide a fitting curve, even if it did not coincide with other peaks.

We consider that this fitting was not necessary. However, and following the reviewer's suggestion, Figure 4c has been modified accordingly.

• The Figures in the main text should be standardized. In Figures 5, 6, 7, 8 and 9, the horizontal coordinate and vertical coordinate inside every Figure should be deleted and the coordinates should be placed on the outside. And please use the same Figure size and presentation mode for all Figures which were presented in the manuscript.

Figures 5, 6, 7, 8 and 9 have been appropriately modified in the revised version of the manuscript. The format has been standardized, showing a homogeneous aspect with the rest of the figures in the work.

• In addition to above problems, the meaning of a, b, c, d, e or f was not clearly shown within Figure 5. It could be considered to show the meaning of a, b, c, d, e or f within Figure. The authors could redraw the XRD pattern of a, b, c, d, e or f into a single Figure, or the authors could divide Figure 5 into two Figures which were marked with (a) and (b). In addition, the unit of the y ordinate in Figure 5 should be changed to (a.u.), and the peak which was represented by "* - Ag NPs" whith tFigure 5 on the left side was not seen clearly, as a result, the existence of Ag could be proved by using Figure 5. Please modify it. We could not find the diffraction peaks of "A-anatase"on the right side of Figure 5. "A-anatase" could be deleted from the right side of Figure 5.

As the reviewer suggests, Figure 5 can be a bit confusing, so it has been modified. We consider that the changes made can contribute to making it easier for the reader to understand it.

• (a) and (b) were not mentioned in the legend of Figure 6. We could not distinguish (a), (b), a and b within Figure 6, please make appropriate modifications.

These changes have been made in the revised version of the manuscript.

• In Figure 7, in addition to above problems, it should also be noted that the y ordinate of Figure 7 should contain“Removal rate of degrading ciprofloxacin (%)" in stead of “% degradation”.

The label suggested by the reviewer for the Y axis is too long and, from an eminently practical point of view, does not fit in the figure. To remedy this situation, the figure caption has been modified to further clarify the results shown in Figure 7.

• Based on the experimental data in Fig. 7, the authors should also provide the adsorption removal rate for a certain period of time under dark conditions. At the same time, the data spectrum of direct photolysis without catalyst should be.

The degradation rates of ciprofloxacin in the absence of a catalyst (photolysis) or in the absence of an irradiation source (catalysis) are less than 7%, this being an insignificant percentage compared to the photocatalytic degradation rates. This information is found in section 2.3 (Stability Tests).

• The first half of the manuscript did not explain whether light was needed during the experiment. And it is not specified whether to use visible light or ultraviolet light. Please specify the specific light irradiation conditions for the experiment in the main text and Figure legend.

The catalytic photodegradation process of ciprofloxacin, as described in section 3.6 (Photocatalytic Experiments), is carried out by irradiation, using a solar simulator made up of two circular lamps that generate an illuminance of 52,000 lux, equivalent to 60 watts. The wavelength profile of this radiation is similar to that of solar radiation (mixture of UV and visible radiation). In order to clarify the experimental conditions, this information has been included in the revised version of the manuscript.

• The y ordinate in Figure 8 was described by"A / A0". Please explain the meaning of "A / A0". If the authors want to express the ratio of concentration to initial concentration, "C / C0" could be used.

In order to clarify any possible doubt that the reader may have, and considering that in many of the published works the term C/Co is used conventionally, Figure 8 has been modified.

• It could be seen from Figure 11 that H2 was finally generated. The authors should provide the methods for calculating the relevant illumination intensity. The author should calculate the light quantum efficiency and the value of "turn over" for producing H2.

The irradiation for the studies of hydrogen production by water splitting was carried out using a solar simulator, whose irradiation power is 100 mWcm^-2, and which allows the use of cut-off filters to select the irradiation wavelength. This information has been included in the revised version of the manuscript.

On the other hand, we have been evaluating the reviewer's suggestion to determine the TON of each catalyst. However, when dealing with heterogeneous catalysts, these measurements are extraordinarily complex and require additional measurements that we cannot perform, so these parameters have not been included in the revised version of the manuscript.

• Author should completely check and revise the format of their manuscript according to the author guidelines of the For example, the format of “2.1.1. FE-SEM and EDS” should be the same as the format of “2.1.2. HRTEM” or “2.1.3. BET analysis” or “2.1.4. XPS analysis”, as a result, there was not 4 spacing before “2.1.1. FE-SEM and EDS” or “2.1.2. HRTEM” or “2.1.3. BET analysis” or “2.1.4. XPS analysis” or “2.1.5. XRD analysis” or “2.1.6. Raman analysis ”. Please make corresponding adjustments.

The reviewer is right. There were some formatting problems that have already been corrected in the revised version of the manuscript.

• Please explain the number "276" in Table 3. "2.1.6" appeared twice in line 195 and line 212 of the manuscript. Please explain the reason or modify it.

Due to formatting problems, the numbering of two consecutive headings was repeated. Sorry for the inconvenience. These errors have been corrected in the revised version of the manuscript.

• The initials of "analysis" which appeared in “1.3. BET analysis” or “2.1.4. XPS analysis” or “2.1.5. XRD analysis” or “2.1.6. Raman analysis ” should be capitalized. Note that the format which appeared before the manuscript and after the manuscript should be unified.

The changes suggested by the reviewer have been addressed.

• In line 414, "25oC" appeared. Please explain the meaning of "oC" which was different from "℃" which appeared in line 426. Did the author create a new symbol? Please explain it.

This is a formatting error. Obviously oC represents ºC. All symbols and abbreviations have been revised in the new version of the manuscript.

• Please provide the possible degradation path of the pollutant during the experiment. Please provide the intermediate products during the degradation process of ciprofloxacin.

The possibility of determining the compounds generated in photodegradation, as indicated by the reviewer, would be of great relevance to support the degradation mechanism. However, at the moment neither we nor our collaborators have equipment available that allows us to obtain this information. In fact, we are currently in the process of installing a UPLC-MS/MS that will allow us to carry out this type of study in a few months, so we hope to be able to include this type of information in future papers.

• Please provide the relevant UV-Vis diffuse reflectance absorption spectra of the catalysts. Please provide the energy band width of each catalyst which was involved in the article.

The authors acknowledge the importance of knowing and reporting the bandgaps of the modified catalysts. However, the instrument used for this research (Shimadzu UV-1800PC) does not have the capability to do conduct UV-Vis diffuse reflectance. With that being said, it is estimated that the band gap of the synthesized Ag@TiO₂-MoS₂ could be in the range of 2.40 eV – 2.10 eV. This estimation is based on studies made by Lv, J. and group (2018), and Kumar et. Al (2018).

Lv, J., Miao, R., Zhang, M. et al. 2018. Few-layers MoS2 sensitized Ag–TiO2 nanocomposite thin film for enhancing photocatalytic activity. J Mater Sci: Mater Electron 29, 16282–16288. https://doi.org/10.1007/s10854-018-9717-5) is estimated that the bad.

Paul, K.K., Sreekanth, N., Biroju, R.K., Narayanan, T.N., & Giri, P.K. 2018. Solar light driven photoelectrocatalytic hydrogen evolution and dye degradation by metal-free few-layer MoS2 nanoflower/TiO2(B) nanobelts heterostructure. Solar Energy Materials and Solar Cells. DOI:10.1016/J.SOLMAT.2018.05.056

• Please provide error bars for all degradation curves which were contained in the manuscript.

The estimated error in the degradation measurements (Figure 7) is ca. 5%. Each figure contains four catalytic degradation profiles, so adding error bars to each value in the figure can make it very difficult to understand the results. To avoid overcomplicating the figure and considering the reviewer's suggestion, information about the relative error of each measurement has been added to the figure caption.

• In addition, a polishing of the English grammar would be required in order to improve the readability of the manuscript.

Following the reviewer's recommendation, a comprehensive revision of the manuscript has been carried out to correct minor deficiencies in English.

Author Response File: Author Response.pdf

Reviewer 2 Report

In this paper, the authors report on the photocatalytic activity of silver-based catalysts containing different amounts of molybdenum disulfide. The dual-use of the catalysts was reported: photocatalytic degradation of the ciprofloxacin and the hydrogen production via water splitting.

Overall I would say research is well-done, no need for additional experiments, and only minor corrections need to be made:

1) Section 2.1.8., lines 302, 305, 318, 319, 322, etc. numbers representing hydrogen production should be written without commas.

2) Numbers in Table 4 and Table 5 should be written without commas.

3) I suggest several language improvements throughout the whole manuscript: crystallographic should be replaced with crystalline as you are not working with monocrystals; SEM/TEM images replaced with SEM/TEM micrographs; bare replaced with unmodified/pristine/reference sample.

Overall, after correcting the above addressed, I would suggest publishing this manuscript in Catalysts.

Author Response

Response to the comments of reviewers and list of changes introduced in the revised version

Reviewer #2:

• 1) Section 2.1.8., lines 302, 305, 318, 319, 322, etc. numbers representing hydrogen production should be written without commas.

Changes made as suggested by the reviewer.

• 2) Numbers in Table 4 and Table 5 should be written without commas.

Changes made as suggested by the reviewer.

• 3) I suggest several language improvements throughout the whole manuscript: crystallographic should be replaced with crystalline as you are not working with monocrystals; SEM/TEM images replaced with SEM/TEM micrographs; bare replaced with unmodified/pristine/reference sample.

All changes suggested by the reviewer have been considered and the manuscript has been modified accordingly. The English has been carefully revised to improve grammar and make it easier for the reader to understand the research.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments to the Author Manuscript Catalysts-1561028

The manuscript entitled ‘Silver and molybdenum disulfide photocatalysts for the production of hydrogen and degradation of ciprofloxacin’ by Machín et al. focuses on the synthesis of the silver-based catalysts containing different amounts of molybdenum disulfide on the TiO₂ support (prepared nanowires and commercially available TiO₂) and use them as an effective catalysts in the reaction of ciprofloxacin degradation as well as the production of hydrogen via water splitting. Very interesting and well-carried study. There are some points which must be edited or clarified by providing additional information or comments:

1. Title of proposed manuscript should be concretized, due authors used composites based on the synthesized and commercial TiO₂ nanowires with incorporated silver nanoparticles and molybdenum disulfide. Please, elaborate it.
2. The authors should write the complete terms of all abbreviations (including the instruments) before the first use in the abstract and main manuscript: i.e. FE-SEM, HRTEM, BET, XRD, Raman and XPS abbreviations in the last line of abstract section.
3. Introduction section: the authors should clearly explain the innovation and importance of their work on the introduction of the manuscript. They should justify the value of the work and compare their work with previously similar published papers. The introduction section needs to be elaborated.
4. All prepared composite catalysts were excellent identified. But, the biggest lack of this study - is missing of any statistical analysis in all catalytic experiments. For example, in Figure 7, which shows data on the degree of decomposition of ciprofloxacin in the presence of the obtained catalysts, it is very difficult to conclude about a more higher or lower catalytic activity of studied composite. All values of the last column of Table 2 are within the standard deviation. This point needs to be explained. For a better demonstration of the differences between studied catalysts, a calculating the values of the reaction rate constant is suggested. Authors are encouraged to provide the values of this parameter.
5. Please provide the value of the catalysts testing temperature in this study. Did you control it for all experiments and how did you performed it? And my suggestion is to add in the revised manuscript information about activation energy values. Ea data will clearly demonstrate the preference of synthesized catalyst with enchased photocatalytic activity.
6. Section 2.1.8: line#285. Could explain why photocatalytic hydrogen production was investigated at the different wavelengths (i.e. 320, 400, 500, and 600 nm)?
7. Conclusion section should be elaborated. Again authors stated about “Silver-based catalysts with different amounts of MoS₂ loadings (5, 10, 20 wt.%)”… But main part of prepared catalysts is TiO₂ support! You have to change this mistake in conclusion section as well as in other sections.

Our decision on this manuscript – Major revision. Only after making substantial changes in article it could be recommended for publication

Author Response

Response to the comments of reviewers and list of changes introduced in the revised version

Reviewer #3:

• Title of proposed manuscript should be concretized, due authors used composites based on the synthesized and commercial TiO₂ nanowires with incorporated silver nanoparticles and molybdenum disulfide. Please, elaborate it.

The reviewer is correct, so the title of the paper has been changed in the revised version of the manuscript.

• The authors should write the complete terms of all abbreviations (including the instruments) before the first use in the abstract and main manuscript: i.e. FE-SEM, HRTEM, BET, XRD, Raman and XPS abbreviations in the last line of abstract section.

Changes made as suggested by the reviewer.

• Introduction section: the authors should clearly explain the innovation and importance of their work on the introduction of the manuscript. They should justify the value of the work and compare their work with previously similar published papers. The introduction section needs to be elaborated.

All text has been carefully reviewed, including information that may help understand the scope of our investigation. We consider that the introduction is sufficiently detailed although, to clarify the final objective of the investigation, an additional text has been introduced at the end of the section.

• All prepared composite catalysts were excellent identified. But, the biggest lack of this study - is missing of any statistical analysis in all catalytic experiments. For example, in Figure 7, which shows data on the degree of decomposition of ciprofloxacin in the presence of the obtained catalysts, it is very difficult to conclude about a more higher or lower catalytic activity of studied composite. All values of the last column of Table 2 are within the standard deviation. This point needs to be explained. For a better demonstration of the differences between studied catalysts, a calculating the values of the reaction rate constant is suggested. Authors are encouraged to provide the values of this parameter.

We consider that there has been some error in what was argued by the reviewer. Table 2 corresponds to percentages of degradation, which are certainly very high and well, well above ca. 5% that corresponds to the deviation of the measurements. However, this deviation data has been introduced in the revised version of the manuscript to clarify the relevance of the results obtained.

As suggested by the reviewer, the pseudo first-order kinetic constants have been determined, together with the correlation coefficients (R²), and these results have been included as Table 2 of the revised version of the manuscript.

• Please provide the value of the catalysts testing temperature in this study. Did you control it for all experiments and how did you performed it? And my suggestion is to add in the revised manuscript information about activation energy values. Ea data will clearly demonstrate the preference of synthesized catalyst with enchased photocatalytic activity.

All measurements of photocatalytic degradation of ciprofloxacin were performed at 22 °C. The measurements corresponding to the photocatalytic hydrogen production were carried out at 20 ºC, under fully controlled conditions and using a thermostatic system to avoid possible effects derived from the heating of the reaction mixture. To clarify possible doubts in this regard, this information has been included in the revised version of the manuscript.

What the reviewer suggests about determining the Ea of the processes would certainly be interesting. However, the photodegradation and hydrogen production reactions of this research have been carried out keeping the reaction systems thermostated at constant temperature, so it is not possible to determine the Ea of any of these processes.

• Section 2.1.8: line#285. Could explain why photocatalytic hydrogen production was investigated at the different wavelengths (i.e. 320, 400, 500, and 600 nm)?

The purpose of considering various irradiation energies was to understand how different wavelengths influence hydrogen production. Catalysts show different radiation absorption profiles, depending on the composition, and this profile should have an effect, as has been shown, on the efficiency of the process.

• Conclusion section should be elaborated. Again authors stated about “Silver-based catalysts with different amounts of MoS₂ loadings (5, 10, 20 wt.%)”… But main part of prepared catalysts is TiO2 support! You have to change this mistake in conclusion section as well as in other sections.

As the reviewer suggests, the text has been modified appropriately. We have always considered the activity of metal nanoparticles very relevant, so when we have referred to catalysts we have done so in this sense. However, the reviewer is correct and his/her suggestion has been addressed, modifying several sections in the revised version of the manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Author Response

Response to the comments of reviewers

Reviewer #1:

1. "It could be seen from Figure 11 that H2 was finally generated. The authors should provide the methods for calculating the relevant illumination intensity. The author should calculate the light quantum efficiency and the value of "turn over" for producing H2." The author should try to answer this question.

This question was answered in the first review, including additional information in the revised version of the manuscript. However, to clarify any possible doubts, the production of hydrogen is carried out by means of a solar simulator, which provides the irradiation power in the absence of filters (whose value is 100 mWcm^-2). When the different cut-off filters are used, only radiation of a certain wavelength reaches the reactor, and this radiation power has not been measured. This additional information has been included in the revised version of the manuscript (see section 3.6). Regarding the other comment from the reviewer, in the case of heterogeneous catalysts, the measurement of TON is complex and requires additional measurements that we cannot perform, so this information has not been included in the revised version of the manuscript.

2. "Please provide the possible degradation path of the pollutant during the experiment. Please provide the intermediate products during the degradation process of ciprofloxacin." The author did not answer this question.

Currently, we are unable to perform these measurements, as previously argued to the reviewer. The possibility of determining the compounds generated in photodegradation would be of great relevance to support the degradation mechanism, but at the moment, neither our collaborators nor we have equipment that allows us to obtain this information. We will be able to carry out this type of measurement within a few months, once the installation of a UPLC-MS/MS is finished.

3. "Please provide the relevant UV-Vis diffuse reflectance absorption spectra of the catalysts. Please provide the energy band width of each catalyst which was involved in the article." The author shouldtry to accomplish this test.

This same question was raised by the reviewer and we believe it was adequately answered. For this investigation, a Shimadzu UV-1800PC spectrophotometer was used. This instrument does not allow bandgap measurements. However, and as the reviewer previously argued, it is estimated that the band gap of the synthesized Ag@TiO₂-MoS₂ is in the range of 2.40 eV – 2.10 eV. This estimation is based on studies made by Lv, J. and group (2018), and Kumar et. Al (2018).

Lv J, Miao R, Zhang M et al. 2018. Few-layers MoS₂ sensitized Ag–TiO₂ nanocomposite thin film for enhancing photocatalytic activity. J Mater Sci: Mater Electron 29, 16282–16288. https://doi.org/10.1007/s10854-018-9717-5) is estimated that the bad.

Paul, K.K., Sreekanth, N., Biroju, RK., Narayanan, T.N., & Giri, P.K. 2018. Solar light driven photoelectrocatalytic hydrogen evolution and dye degradation by metal-free few-layer MoS₂ nanoflower/TiO2(B) nanobelts heterostructure. Solar Energy Materials and Solar Cells. DOI:10.1016/J.SOLMAT.2018.05.056.

4. "In addition, a polishing of the English grammar would be required in order to improve the readability of the manuscript." The author should try to improve the English grammar.

The English has been revised again by a native English speaker.

Author Response File: Author Response.pdf

Reviewer 3 Report

Undoubtedly, in the revised version of the manuscript, the authors tried to take into account all the comments and recommendations of the reviewers, which significantly improved the manuscript itself in the toga.

However, I still have a few unresolved issues that require more thorough explanation by the authors in the second round of review:

Reviewer comment R1

All prepared composite catalysts were excellent identified. But, the biggest lack of this study - is missing of any statistical analysis in all catalytic experiments. For example, in Figure 7, which shows data on the degree of decomposition of ciprofloxacin in the presence of the obtained catalysts, it is very difficult to conclude about a more higher or lower catalytic activity of studied composite. All values of the last column of Table 2 are within the standard deviation. This point needs to be explained. For a better demonstration of the differences between studied catalysts, a calculating the values of the reaction rate constant is suggested. Authors are encouraged to provide the values of this parameter.

Authors responce:

We consider that there has been some error in what was argued by the reviewer. Table 2 corresponds to percentages of degradation, which are certainly very high and well, well above ca. 5% that corresponds to the deviation of the measurements. However, this deviation data has been introduced in the revised version of the manuscript to clarify the relevance of the results obtained.

As suggested by the reviewer, the pseudo first-order kinetic constants have been determined, together with the correlation coefficients (R2), and these results have been included as Table 2 of the revised version of the manuscript.

#Reviewer comment R2

I’m still not finding any deviation values in revised version and my quote was not answered well. The next question that is still not resolved  is why all samples with a 20% loading of MoS2 show a decrease in the values of Degradation rate (table 2) and k (table 3)? Authors should add an appropriate explanation in manuscript.

Reviewer comment R1

Section 2.1.8: line#285. Could explain why photocatalytic hydrogen production was investigated at the different wavelengths (i.e. 320, 400, 500, and 600 nm)?

Authors responce:

The purpose of considering various irradiation energies was to understand how different wavelengths influence hydrogen production. Catalysts show different radiation absorption profiles, depending on the composition, and this profile should have an effect, as has been shown, on the efficiency of the process.

#Reviewer comment R2

Why authors did not provide any explanation in revised manuscript& I think that this selection of wavelengths as well as its impact on the hydrogen production should be more discussed.

Author Response

Response to the comments of reviewers

Reviewer #3:

I’m still not finding any deviation values in revised version and my quote was not answered well. The next question that is still not resolved is why all samples with a 20% loading of MoS2 show a decrease in the values of Degradation rate (table 2) and k (table 3)? Authors should add an appropriate explanation in manuscript.

Taking into account the reviewer's comment, Table 2 was modified by truncating the ciprofloxacin photodegradation values and entering the estimated error data as a footnote.

Regarding the other issue raised by the reviewer, the effect of increasing MoS₂ loading on the catalyst is not unusual. Different components of a catalyst contribute differently to its efficiency. 20% MoS₂ is an apparently high load that, in the case of photodegradation reactions, can cause the catalytic reaction to proceed differently than when this cocatalyst is present in a lower proportion. This behavior, however, does not occur in the production of hydrogen, whose maxima are shown in catalysts that have 20% MoS₂. To elucidate the effect of MoS₂ on the catalytic photodegradation of ciprofloxacin, it would be necessary to evaluate the intermediate compounds generated in the process, something that we currently cannot do in the laboratory. To clarify this fact, the conclusions section has been modified accordingly.

Why authors did not provide any explanation in revised manuscript& I think that this selection of wavelengths as well as its impact on the hydrogen production should be more discussed.

The purpose of considering various irradiation energies was to understand how different wavelengths influence hydrogen production. As seen in Figure 9 of the manuscript, the maximum hydrogen production is observed under irradiation at 400 nm, although the values obtained are quite similar to those recorded under irradiation at 500 nm. The use of filters allows us to know the dependency of the process depending on the radiation frequency. As can be seen, the catalysts are capable of absorbing visible radiation and promoting water splitting, this being the ideal behavior when what we seek is to carry out the generation of hydrogen through solar radiation, mostly irradiating in the visible region. To clarify this information, the manuscript has been modified (lines 1576-1580, section 2.5).

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

Authors respond for all my queries and in present for this manuscript could be recommended for publication