In my opinion, this manuscript needs revision, based on the following comments:

1) The text needs to be edited for possible editorial corrections.

2) Please include one qualitative statement about the work importance + one statement on current and future prospect of hydrogen production.

3) The contribution of the work to the literature needs to be better highlight in the introduction.

4) The review paper needs to include more previous works. Their drawbacks should be also mentioned somehow.

5) I like the authors to add one or two paragraphs to the introduction section, and discuss about various hydrogen production methods, giving a big picture of the available strategies, and eventually narrow their discussion to water splitting for producing hydrogen. They might use the suggested refs below to address this comment.

6) Would you please better describe the limitations and advantages of the particular approach of water splitting for producing hydrogen discussed in this review work.

7) A simple process diagram for the particular hydrogen production technique described in this review might need to be included.

8) The practical and theoretical challenges of the hydrogen production method need a little more work.

9) I like to see a brief discussion on the environmental, safety, and economic aspects of the hydrogen production method described in this review.

10) Can you please further discuss about relative importance of input parameters/conditions in water splitting for producing hydrogen using visible light?

11) I was wondering how the Znln2S4-based photocatalysts are screened/selected for hydrogen production.

12) Can you further discuss about the activity and deactivation of the Znln2S4-based photocatalysts , please?

13) There are some good documents in the literature that focus on various hydrogen production methods, Znln2S4-based photocatalysts, water splitting for producing hydrogen, climate change, and so on. In my opinion, a brief discussion on various hydrogen production methods and their differences (advantages and disadvantages) with the particular one discussed in this review should be included in this paper. 1 to 2 good paragraphs should be enough.

14) To address part of the comments above, I suggest you to go through (and include) the following documents and make a link between your work and previous studies. They can also make the background sections stronger.

** Semiconductor Nanomaterial Photocatalysts for Water-Splitting Hydrogen Production: The Holy Grail of Converting Solar Energy to Fuel. Nanomaterials 2023, 13, 546.

** Reaction systems for solar hydrogen production via water splitting with particulate semiconductor photocatalysts. Nat. Catal. 2019, 2, 387–399.

** A comprehensive review on hydrogen production and utilization in North America: Prospects and challenges. Energy Conversion and Management 269, 115927, 2022.

** Photo-assisted splitting of water into hydrogen using visible-light activated silver doped g-C3N4 & CNTs hybrids. Int. J. Hydrogen Energy 2020, 45, 31574–31584.

** CoNi Bimetal Cocatalyst Modifying a Hierarchical ZnIn2S4 Nanosheet-Based Microsphere Noble-Metal-Free Photocatalyst for Efficient Visible-Light-Driven Photocatalytic Hydrogen Production. ACS Sustainable Chem. Eng. 2019, 7, 24, 20190–20201.

** All solid-state Z‑scheme CeO2/ZnIn2S4 hybrid for the photocatalytic selective oxidation of aromatic alcohols coupled with hydrogen evolution. Applied Catalysis B: Environmental 2020, 277 , 119235.

** Development of an integrated structure of hydrogen and oxygen liquefaction cycle using wind turbines, Kalina power generation cycle, and electrolyzer. Energy, Volume 221, 15 April 2021, 119653.

** A facile synthesis of a ZIF-derived ZnS/ZnIn 2 S 4 heterojunction and enhanced photocatalytic hydrogen evolution. Dalton Transactions 2020, 49 (31) , 10816-10823.

** One-pot sulfurized synthesis of ZnIn2S4/S,N-codoped carbon composites for solar light driven water splitting. International Journal of Hydrogen Energy 2021, 46 (34) , 17697-17707.

15) The quality of the figures needs improvement.

16) A nice figure or flowchart/diagram is needed to show the structure of this review.

17) The modeling and experimental studies on this particular subject might need to be better explained. In this context, you might also talk about the characterization of Znln2S4-based photocatalysts, and challenges related to design, scale up, and so on.

18) Figures 5-7: Would you please better explain these figures and the behaviors.

19) I like to see a better discussion on the current and future aspects of Znln2S4-based photocatalysts in water splitting for producing hydrogen using visible light.

20) A few recommendations might be needed for future work.

21) The conclusions section needs to have a better flow and structure.

22) In my opinion, a review paper needs to provide clear "messages" to technical readers, in each section. One way of doing so will be to answer the following questions at the end of each section:

E) What are the 2-3 things that a reader should take away from what is discussed in each section?

F) What still needs to be done, or/and what are the limitations of the topic/model in terms of application, theory, etc., or this is a closed topic and mechanisms and physics well understood and the matter has become a classical topic? Also, in writing each section, you may want to answer this question for yourselves, what did you add to the literature, by integrating the material? or you just integrated the material (note just integrating material will not constitute a good review)?

23) I think that a good review needs to have a few informative Tables and Figures that include the previous studies or data available in the literature. This should highlight a part of the important findings attained from the previous investigations on the discussed topics. You might already talked about the important aspects in the text, but technical readers like more to see tables or figures for better understanding and connecting to the discussion.

24) Please double- check all the refs.

Some of my comments (particularly comments no.11 to 17) have not been addressed adequately. Therefore, I recommend the authors to carefully address them through a clear and understandable approach.