Effect of CTAB on the Morphology of Sn-MOF and the Gas Sensing Performance of SnO₂ with Different Crystal Phases for H₂ Detection

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper presents a simple strategy to improve the gas-sensitizing properties of SnO2 to H2 by adjusting the crystalline phase composition of SnO2. The article does a lot of work, but leaves a lot to be desired, so my recommendation is  major revisions.

1. The formatting of the article needs to be standardized, such as subscripts.
2. The quality of the abstracts needs to be improved. The abstract needs to highlight more clearly the innovations and key findings of the study.
3. What is innovative about the study compared to other similar studies?
4. The K-value method was used for the calculation of the mixing phase ratio, but no specific calculation steps or margins of error were described, so it is recommended that additional methodological details be added.
5. Humidity is an important interfering factor in practical applications, but the H₂ response at different humidity levels was not tested in the paper, and additional relevant experimental data or discussion is needed.
6. Figure 7 is a bit simple and needs additional detail.
7. The table comparing the performance with similar recent work is missing, and it is recommended that a table be added to highlight the response values, detection limits, and other advantages of this study.
8. Additional reproducibility data (e.g., error bars) are recommended to demonstrate the reliability of the results.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Manyi Liu et al. presented in this manuscript a method to enhance H2 sensing properties of SnO2, tuning its crystalline phase thanks to the use of CTAB. 

The work can be of interest; the introduction presents the state of art and the novelty of the proposed method. Nevertheless, some aspects lack clarity, more information should be disclosed, and additional measurements are required, before the current work can be considered for publication. In details, my comments are as follow: 

1. Carefully check English and grammar through the whole manuscript. 
2. Paragraph 2.2: at lines 117-118 authors wrote “The detailed methodologies and evaluation procedures were described in the SI.”. Nevertheless, no SI file is submitted. Please provide all the necessary information. For XPS: please disclose how the system is calibrated, at which pressure and which power has been used to collect data and which fitting procedure has been exploited (i.e. which type of background, type of function...). 
3. Paragraph 2.3: more information about the gas sensing measurements should be disclosed: are the measurements performed in a close chamber? Which is the volume? How is the chamber fed and then purged? A scheme of the set-up as well as on the working circuit of the sensor should be added. 
4. SEM analysis: a proper statistical analysis to assess the size of the nanostructures should be performed and added. 
5. Figure 4a: please identify in the graph all the detected peaks and properly comment on them in the manuscript. 
6. Paragraph 3.2 - XPS: which is the R2 value for each fitting? They should be similar to properly compare the data. 
7. Figure 5e and main text about LOD: authors present a linear fit of the calibration curve. Nevertheless, at low concentration the fit does not follow the experimental data. A two-regime fit or a different curve (maybe Freundlich isotherm) should be considered and the LOD should be re-evaluated in the low concentration regime. Finally, error bar should be reported for the experimental data. 
8. Figure 5g: selectivity tests have been performed considering 100 ppm, for H2 and for some other analytes. Nevertheless, the selectivity is not proved. Indeed, for instance, the response to CO is quite high; for 100 ppm the response is about 2 and 4, for SnO2-NC and SnO2-C, respectively. According to data reported in panels d and e of the same figure, these responses are obtained also for 50 ppm of H2. These demonstrate that the sensors are not selective and cannot really discriminate between H2 and CO. The same comment is valid for the other analytes, including H2S. Can the authors propose a method to achieve selectivity and properly discuss it in the manuscript? 
9. Additionally, about selectivity:  can the author discuss in the manuscript the criteria behind the choice of these analytes? Are they interfering of H2 in particular applications? 
10. Authors wrote that the stability over time of the response is proven, nevertheless, these data are not reported. Please provide the SI file and all the data mentioned in the manuscript. 
11. Benchmarking for LOD, response, and response/recovery time with current literature should be added. 
12. Relative humidity (RH) is a very important parameter to consider when developing gas sensors; indeed, it can highly influence a sensor performance. In a real application RH value can range from 10% up to 70-80%. Firstly, authors should disclose the humidity value during their measurements; secondly influence of RH should be also properly discussed in the manuscript, especially in reference on how it can influence the sensing mechanism. 
13. References are not in the correct format. 
14. Figures should be placed after they are cited in the manuscript.

Comments on the Quality of English Language

Grammar is not always correct (for instance incorrect verb tenses).

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have carefully revised the paper based on the reviewers' comments and I find it acceptable for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors carefully revised the manuscript, taking into account the comments previously made. They improved both quality and clarity in the results presentation and properly discussed all the issues. 

I now think that the work can be accepted for publication.