Thermal Sprayed Protective Coatings for Bipolar Plates of Hydrogen Fuel Cells and Water Electrolysis Cells

Round 1

Reviewer 1 Report

Dear Authors,

Some parts of the text are hard to understand. For example "the decomposition product
(La2O3) can deteriorate the high-temperature oxidation resistance of as-sprayed coating
by promoting absorption/transport of water molecules. Similarly, phase decomposition of
Mn-Co spinel will occur and decrease the electrical conductivity due to formation of the
(Mn,Co)O rock salt phase." I

Please see the comments to the authors.

Author Response

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Reviewer 2 Report

Thermal Sprayed Protective Coatings for Bipolar Plates of Hydrogen Fuel Cells and Water Electrolysis Cells

The manuscript presents the review the various coatings of bipolar plates in particular particular emphasizing on the effect of spraying processes on coating effectiveness. Author has prepared a good review, however this manuscript required more through revision within depth discussion. The manuscript can be considered to be publication with minor revisions.

1.      Can author include more discussion on protective coating on bipolar plates?

2.      Can author provide a comprehensive table on the various method used to clearly understand the differences in the process on various key parameters?

3.      Please provide an additional table/chart with preferred method trend among the researchers based on performance with discussion.

NA

Author Response

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Reviewer 3 Report

The review is devoted to an urgent problem related to the development of hydrogen fuel cells and elements for water electrolysis. For commercialization, it is necessary to reduce the cost of manufacturing the main components of devices - bipolar plates (BPs) by replacing expensive materials used with inexpensive and easy-to-process ones (steels, aluminum, etc.). The review provides a systematic review of advanced technologies for thermal spraying of protective coatings of electrodes on BPs, preventing their oxidation and corrosion. These include atmospheric plasma spraying (APS), vacuum plasma spraying (VPS) and high-speed oxygen-fuel spraying (HVOF). Rare-earth perovskite and spinel oxides, Nb and Ti/Nb, low-melting metals or non-oxide ceramic and cermet materials, etc. are mainly considered as materials. A comparison of methods and methods of their implementation shows that the qualities of the coatings obtained are determined by the composition of the sprayed material, as well as their structure. The review substantiates the advantages and disadvantages of the methods and indicates the factors influencing the quality of coatings.

The article summarizes the main results on an important and urgent problem, substantiates the advantages of spraying methods and materials used, and contains a list of the main published works. It will be of considerable interest to specialists. It is a rare case, but the article, in the opinion of the reviewer, can be published in present form. As a suggestion, we can only recommend that the authors compare the test data of promising BPs with similar data for BPs that are currently used in fuel cells.

Author Response

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Reviewer 4 Report

A review manuscript on Thermal Sprayed Protective Coatings for Bipolar Plates of Hydrogen Fuel Cells and Water Electrolysis Cells has been proposed. The manuscript is written in simple, understandable language for a wide range of readers, is well structured and contains a large number of references to previously published works.

I recommend accepting the article in its current form.

However, from a technical point of view, the article contains pictures in poor quality (all of the ones shown). Particular attention should be paid to Figure 5b, c, which displays two curves on each (judging by the legends of the curves there should be 4 for 5b, 5c).

Minor editing of English language required

Author Response

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Reviewer 5 Report

This review refers to numerous methods of thermal spraying technologies such as atmospheric plasma spraying (APS), vacuum plasma spraying (VPS) and high-velocity oxygen-fuel (HVOF) spraying with an aim to prepare coatings of bipolar plates. Several parameters like spraying processes, materials and microstructure configuration, temperature and velocity of particle are examined and their influence on the performance of the coating is discussed and the necessity of the level of controlling of each factor is estimated.

The review is interesting and useful and it is something that will occupy a gap in the market of Coatings. It can be published at the respective journal as long as the direction of using the fabricated coatings in photonic applications [1-3], a side that has not been particularly stressed in the work at hand. 

[1] Rapid fabrication of photonic crystal patterns with iridescent structural colors on textiles by spray coating, Dyes and Pigments, 2021.

[2] Closed–Form Solution to the Scattering of a Skew Strip Field by Metallic Pin in a Slab, Progress In Electromagnetics Research, 2008.

[3] Thin-film coating methods: A successful marriage of high-quality and cost-effectiveness- A brief exploration, Coatings, 2022.

Author Response

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