Brief Review on High-Temperature Electrochemical Hydrogen Sensors

Round 1

Reviewer 1 Report

The author provided a thorough review of electrochemical hydrogen sensors by giving a tutorial introduction of the principles of potentiometric, amperometric, and combined amperometric-potentiometric sensors as well as summarizing recent development and applications correspondingly. The author also described a two-stage procedure in amperometric sensor to detect hydrogen and steam in atmospheric air. The review is beneficial to the research community, and it is recommended to be accepted for publication in Catalysts after addressing the following comments. 

 

1. Please consider revising the title of the manuscript as the review is not mainly focusing on high temperature engineering of sensors. 

Author Response

Reviewer 1

The author provided a thorough review of electrochemical hydrogen sensors by giving a tutorial introduction of the principles of potentiometric, amperometric, and combined amperometric-potentiometric sensors as well as summarizing recent development and applications correspondingly. The author also described a two-stage procedure in amperometric sensor to detect hydrogen and steam in atmospheric air. The review is beneficial to the research community, and it is recommended to be accepted for publication in Catalysts after addressing the following comments.

1. Please consider revising the title of the manuscript as the review is not mainly focusing on high temperature engineering of sensors.

Thank you for your positive evaluation. Concerning the title, the review is exclusively focused on high-temperature hydrogen sensors, as can be verified by the discussed works. Only in the first discussed work, in subsection 2.1.1 (ref. 23), lower temperatures were supplementary examined (lower limit 200 ^oC) for the experiment. Even there, the authors focused their analysis on evaluating the type of conduction of the tested electrolyte at high temperatures (<600 ^oC). Therefore, we decided not to change the title in terms of the identification “high-temperature” for the reviewed sensors. We have revised the manuscript title to: “Brief review on high-temperature electrochemical hydrogen sensors”.

Reviewer 2 Report

In this manuscript, the authors have reviewed the recent advances in the development of hydrogen sensors based on solid oxide electrolytes (operating at high temperatures), in particular oxygen ion and proton conductors. Particularly, the principles of operation and the applied solid electrolytes and electrodes of the high-temperature hydrogen sensors are highlighted. This work is well organized, which can be published in Catalysts after a minor revision by addressing the following comments.

1          In the introduction section, the photo(electro)catalysis routes for H2 production should be mentioned and some new references can be referred such as Materials Today Energy 23 (2022) 100896; Materials Today Energy 23 (2022) 100899.

2          More relevant references about proton-conducting solid electrolytes and electrodes for potential application in hydrogen sensors should be addressed and discussed including Journal of Materials Chemistry A 10 (2022) 5381-5390.

Author Response

Reviewer 2

In this manuscript, the authors have reviewed the recent advances in the development of hydrogen sensors based on solid oxide electrolytes (operating at high temperatures), in particular oxygen ion and proton conductors. Particularly, the principles of operation and the applied solid electrolytes and electrodes of the high-temperature hydrogen sensors are highlighted. This work is well organized, which can be published in Catalysts after a minor revision by addressing the following comments.

1. In the introduction section, the photo(electro)catalysis routes for H₂ production should be mentioned and some new references can be referred such as Materials Today Energy 23 (2022) 100896; Materials Today Energy 23 (2022) 100899.

The current article aims to provide an overview of the basic principles of high-temperature electrochemical hydrogen sensors. Therefore, we tried to maintain a relatively small text range, highlighting the emergence of hydrogen detection in the forthcoming hydrogen economy and the principles of the electrochemical hydrogen sensors applied for this purpose. In this direction, we did not focus on hydrogen production (HER). Including such information in the introduction would seem irrelevant to the following content.     

2. More relevant references about proton-conducting solid electrolytes and electrodes for potential application in hydrogen sensors should be addressed and discussed including Journal of Materials Chemistry A 10 (2022) 5381-5390.

In the present review, our goal was to provide the fundamentals of the high-temperature electrochemical sensors for the detection of hydrogen, including their configuration, principle of operation, and application results. To avoid widening the review, we did not include emerging solid oxide materials (proton or oxygen anion conductors) if not applied for sensing purposes. Moreover, searching on Google scholar, most of the published works that appeared are devoted to hydrogen peroxide and hydrogen sulphide sensors or low-temperature sensors for hydrogen detection. We have found no recent research activity on high-temperature electrochemical detection of hydrogen.

Reviewer 3 Report

The authors investigated amperometric, potentiometric, and combination (amperometric-potentiometric) hydrogen sensors based on solid oxide electrolytes at high temperatures in a review study. The manuscript's main focus was describing the basic features, construction, and components of the solid-state electrodes and electrolytes used in high-temperature hydrogen sensors. The manuscript's topic is interesting. However, the manuscript may be suitable for publishing after a major revision.

The following suggestions have been made to improve the manuscript:

1- The manuscript should be carefully checked and corrected for grammatical, typographical, and punctuation errors.

2- Please consider revising the title of the manuscript so that it accurately reflects its intended objective as a review article.

3- The manuscript abstract seems to be revised and reformulated to reflect the most important findings of the current study. Also, in the abstract section, the authors indicated (and concentrations near 100%). What is meant by this concentration?

4- Many Figures did not appear in the article and were replaced by (Error! Reference source not found), which should be included.

5- The conclusion in its current form seems to be a part of the introduction, and it does not rise to an actual conclusion that contributes to highlighting the most important review results obtained. In addition, the inclusion of recommendations is very important in the review paper.

6- Many of the cited works appear to be outdated, so an update to the list of references is advised. Moreover, self-citation should be reduced.

Author Response

Reviewer 3

The authors investigated amperometric, potentiometric, and combination (amperometric-potentiometric) hydrogen sensors based on solid oxide electrolytes at high temperatures in a review study. The manuscript's main focus was describing the basic features, construction, and components of the solid-state electrodes and electrolytes used in high-temperature hydrogen sensors. The manuscript's topic is interesting. However, the manuscript may be suitable for publishing after a major revision.

The following suggestions have been made to improve the manuscript:

1. The manuscript should be carefully checked and corrected for grammatical, typographical, and punctuation errors.

The manuscript has been double-checked for language errors and corrected where necessary. 

2. Please consider revising the title of the manuscript so that it accurately reflects its intended objective as a review article.

We have revised the manuscript title to “Brief review on high-temperature electrochemical hydrogen sensors” to indicate the type (review) of the article. 

3. The manuscript abstract seems to be revised and reformulated to reflect the most important findings of the current study. Also, in the abstract section, the authors indicated (and concentrations near 100%). What is meant by this concentration?

We have revised the abstract to reflect the review’s findings. The sentence where the phrase ‘and concentrations near 100%’ was referred has been removed, as this case is not considered in the discussed works of our review.

4. Many Figures did not appear in the article and were replaced by (Error! Reference source not found), which should be included.

The error has been corrected according to the reviewer’s comment.

5. The conclusion in its current form seems to be a part of the introduction, and it does not rise to an actual conclusion that contributes to highlighting the most important review results obtained. In addition, the inclusion of recommendations is very important in the review paper.

The reviewer is right. We have revised the concluding remarks section to raise some actual conclusions that highlight the most important results obtained from the different research studies, while an attempt was made to include some recommendations in the discussion in the field of high-temperature hydrogen sensors.

6. Many of the cited works appear to be outdated, so an update to the list of references is advised.Moreover, self-citation should be reduced.

Searching on Google scholar, most of the published works are devoted to hydrogen peroxide and hydrogen sulfide sensors or low-temperature sensors for hydrogen detection. We have found no recent research activity on high-temperature electrochemical detection of hydrogen.

Taking into account the current interest in hydrogen utilization, our goal was to highlight in a review article the most important publications, concerning the electrochemical detection of hydrogen at high temperatures. For this reason, we included all the works that appeared in the last two decades. The reviewer is right; our group has enough contribution to this kind of sensor, which is the reason for the extended self-citation. As can be verified, all the self-citations are directly relevant to the topic.

Round 2

Reviewer 3 Report

Thanks to the authors for completing the revised version of the manuscript.