Current Status of Green Hydrogen Production Technology: A Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This review intends to address the unavoidable key of green hydrogen to assure true energetic sustainability and the current trend to improve the efficiency and safety of the production and transportation of that gas. Since it is a review on a subject of uppermost importance and multiplicatively addressed worldwide, it is required that authors should submit a greater number of citations.

It references the future need for energetic efficiency enhancement in green hydrogen production methods but is mainly restricted to the efficiency of renewable energy lacking in more detail innovative technologies; it misses the determining role of nanotechnologies and the need for incorporation of more physics and less harmful chemical emissions for environmental sustainability.

This review paper is not in a position to be published with this title because it is descriptive and presents nothing new: it is an introduction of the current description not prospecting any mode of innovation. A title of the type " Current status of green hydrogen production technology: A review" would be more appropriate.

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The current manuscript is written in an organized manner way so that it can be accepted after a minor revision:

1.  In the abstract highlight the main aim of the study. The abstract should be condensed a little.  

2. The last portion of the introduction must show some sort of motivation.  

3. Provide more comparison on green hydrogen technologies with latest research citation.  

4. Provide in-depth comparison of different green hydrogen production technologies utilized so far and highlighting their advantages, limitations.  

5. I suggest a table can be added which summarizes the strengths and weaknesses of different technologies  

6. I suggest author should add a section that discusses the economic viability of green hydrogen technologies  

7. Adding more graphical representation such as charts or infographics comparing the different hydrogen production methods

8. There must be a proper numbering of the equations used in the manuscript and a unique pattern must be followed through out the manuscript.

9. The format of the references must be checked properly before revision submission.

10. The conclusions must be renamed as concluding remarks.

11. The overall quality of the figures must be improved.

Comments on the Quality of English Language

minor check spellings are required

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The article in question is a review on the current topic of producing green hydrogen. This is a very important topic in light of the sustainable development of our society. The article examines ways to produce hydrogen using renewable resources and energy, and conducts a comparative analysis of their disadvantages, advantages and potential in the future. The following comments are suggested:

1)      It is worth strengthening the rationale for what makes the review unique and how it differs from publications on the topic.

2)      Regarding the use of wind and solar energy. It is important to discuss how much materials and energy will be required to make energy conversion devices. Do we have enough mineral raw materials and what will be the harm to the environment if we want to switch to using these types of energy? The same applies to the production of electrolyzers.

3)      Аuthors often present the material too generally, based on information from other reviews. Examples include sections 3.2, 3.3., 4.2.2., 5.1, 5.4. More than 20% of references are works of a review nature. It is advisable to refer to original experimental scientific publications and provide specific examples of recent achievements. And based on this analysis, draw conclusions about what has been achieved and what needs to be done.

4)      It will be useful to present hydrogen production volumes in both absolute and relative form in order to understand both the volume and the share of the considered methods in hydrogen production. For example, table 1 «The production of hydrogen from renew-able energy sources is expected to reach between 100,000 and 200,000 tons annually (how much will this be as a percentage of the total volume of generated hydrogen?), contributing to a reduction of 1 to 2 million tons of carbon dioxide emissions per year (What will this be as a percentage of total carbon emissions?).»

5)      please check the correctness of title 3.2. «Photothermal decomposition of hydrogen»

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

This review covers the global development status of hydrogen production at different regions, and a very general description of various production routes, including solar water splitting, biomass-derived techniques, electrolysis, etc. However, a review is very different from an encyclopedia and the author needs to provide much more than just basic working principle. Latest research status, performance data, level of technical maturity, etc., are all missing in the review and there are only 60 references. Therefore, the review doesn’t meet the standards of Sustainability and it’s not suggested to be published.

1.       Many figures and tables require proper citations, such as Figure 1 and Figure 4, if it’s cited from other literatures. Similarly, if the data in Table 3 are from other sources, the source needs to be properly cited as well.

2.       Equation 3 is not properly expressed, as ‘illumination’ is not an energy form.

3.       A Table of content or a briefing of chapter is needed at the beginning to better guide the reader.

4.       The Introduction should begin with research trend in hydrogen at global scale, followed by details in different regions like China, EU, US, etc.

5.       Some figures like Figure 16 need to be re-arranged for clearer presentation.

6.       This review only has 61 references, which is not enough for such a broad topic of hydrogen production, 150-200 references are needed.

7.       When discussing detailed technologies under each category, the author only provides very general introduction of the working principle, like 4.1.2, 4.1.3. This is not sufficient for a review paper and state-of-the-art research status are needed, including energy consumption for hydrogen production, cost, state of development (lab-scale, commercialized, pilot plant demonstration, etc.).

Comments on the Quality of English Language

The manuscript includes many grammar mistakes and a comprehensive proofreading is needed.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The paper was improved and the title changed. 

Thus in my opinion it deserves to be published in this revised version.