Electrolytes in Multiple-Phase Hydrogen Storage Reactions
Round 1
Reviewer 1 Report
This work analogy the kinetics of thermochemical multiphase hydro gen storage reactions with electrochemical multiphase battery reactions, and the hydrogen storage reaction kinetics with and without added electrolytes for Mg2/Sn, NaAlH4, and MgB2 were analyzed. This work is interesting and can provide some new for the field. This work can be accepted after some minor revision.
1. The composition of the electrolyte should be added to abstract and introduction.
2. In the introduction, the previous studies on the influence of electrolytes on MgH2/Sn, NaAlH4 should be mentioned and summarized. Besides, relevant studies should be also cited.
Author Response
We thank the Reviewer for their careful review and have made the following changes to address their comments:
1) The composition of the electrolyte was added to the abstract and introduction.
2) The previous studies on MgH2/Sn and NaAlH4 were mentioned and cited in the Introduction.
Reviewer 2 Report
In this work, authors show the use of electrolytes by describing the kinetic limitations in terms of subjective kinetic temperatures and excess free energies. Using these descriptors, they compare multiphase hydrogen storage reactions with multiphase battery reactions. In this direction, they summarize the influence of electrolytes on MgH2/Sn, NaAlH4 and also give further results for the hydrogenation of MgB2. The difference between electrolyte-based and solid-state diffusion-based interparticle atomic transport between the reacting phases was discussed. Using this analogy, the hydrogen storage reaction kinetics with and without added electrolytes for Mg2/Sn, NaAlH4, and MgB2 were analyzed.
The use of electrolytes to accelerate the reaction kinetics of hydrogen storage materials is a novel idea. Comparing the results with the materials used batteries also provides a more understandable conclusion. The strategy in this study is effective in improving the reaction kinetics and lowering the reaction temperatures of the selected hydrogen storage materials. It can also be applied to other hydrogen storage systems. The authors have used fluent and plain language. Experimental results are well explained. As a result, my opinion is that the manuscript can be accepted as is.
Author Response
We thank the Reviewer for their careful review. No additional changes were made.
Reviewer 3 Report
This paper provides an understanding of the kinetic limitations in terms of subjective kinetic temperatures and excess free energies, and a comparison of multiphase hydrogen storage reactions with analogous multiphase battery reactions.
While the paper doesn't cover the practical aspects of the electrolytes usage in hydrogen storage reactions, the paper can be accepted as it is.
Author Response
We thank the Reviewer for their careful review. Although no specific changes were suggested, we revised the last paragraph of the conclusion to address some of the considerations associated with using electrolytes in a practical system.
Reviewer 4 Report
1 - The literature review is absent. The most recent references are from 2020, 2018 and 2017 (one from each year). The state of the art is important to appreciate the contribution of the work to the field.
2 - The theoretical framework seems sound but can be improved by commenting further on the graphics of figure 1, not only naming the sources of those images, but also describing the functions (or the experimental data, if that is the case) leading to the curves presented.
3 -The expression "previous" in the sections titles 3.1 and 3.2 makes it like authors are publishing previous results. Is that it? Additionally, section 3.3 addresses results from ref. 10. What is really new in this manuscript?
4 - The structure of the manuscript is a bit odd, as the materials and methods are introduced after the results and discussion. As to this section of the manuscript, the authors address to refs. 10 and 11 and only describe the additional MgB2 hydrogenation experiments. A summary of the complete sets of materials and methods would be welcome in this paper.
5 - The relevance of this work, in the perspective of the authors themselves, is diminished when they claim in the conclusions that "The practical aspects of using electrolytes for hydrogen storage reactions were not discussed in detail here". What else would the editor care for if the publication of this work is not useful? And if this work does not present new results, why should it be considered to be published?
A few language flaws compromise the quality of the manuscript. Please revise it carefully.
Author Response
We thank the Reviewer for their careful review and have made the following changes to address their comments:
1) In an effort to support the literature review and better cover the state of the art, 10 additional references were included and discussed throughout the paper. The majority of these new references were published between 2021-2023
2) The experimental data shown in Figure 1a is experimental data (previously unpublished). To better clarify this point we have added the following sentence to section 2.1 (before the figure): “As shown in Figure 1a for a typical formulation of a mechanically milled mixture of 2MgH2 + Si undergoing a constant heating ramp (2 °C/min), the onset of the desorption reaction occurs at ~270 °C.” In addition, the figure caption was also modified to further clarify this point.
3) We recognize that the term “previous” in the section titles may be confusing. Section 3.1 was changed to “Analysis of the electrolyte assisted MgH2/Sn hydrogen storage reaction using ∆GK” and Section 3.2 was changed to “Analysis of electrolyte assisted NaAlH4 dehydrogenation using the Avrami-Erofe’ev model”. In addition, in the 3rd paragraph of Section 3.3, the first sentence was modified to further clarify this point: “In this work, we present new results where lower pressures were explored”
4) The Materials and Methods are described after the Results and Discussion as specified in the template. The first sentence of the Materials and Methods section was modified to clarify that additional details are available in references 1 and 2: “The materials and methods including the Sieverts apparatus, the 1000 bar hydrogenation system, and the 11B NMR setup used for the MgH2/Sn, MgB2, LiAlH4, and NaAlH4 experiments have been described completely in Refs 1 and 2.”
5) The last paragraph of the conclusion was rewritten to better clarify the relevance of this work and the important next steps for achieving a practical system.
Reviewer 5 Report
This article discusses using electrolytes to enhance the kinetics of thermochemical multiphase hydrogen storage reactions, drawing an analogy to electrochemical multiphase battery reactions. The difference between electrolyte-based and solid-state diffusion-based atomic transport is explored, and the kinetics of hydrogen storage reactions for various compounds are analyzed. Overall, this paper is nicely written and the results are promising. Thus, this article is recommended for publication in this journal.
Author Response
We thank the Reviewer for their careful review. No additional changes were made.
Round 2
Reviewer 4 Report
The changes made addressed all my concerns.
