Recent Advances in Homogeneous/Heterogeneous Catalytic Hydrogenation and Dehydrogenation for Potential Liquid Organic Hydrogen Carrier (LOHC) Systems

Round 1

Reviewer 1 Report

The review article by Park and coworkers summarizes the recent advances in catalytic transformation of LOHCs to produce hydrogen, a topic that has received increasing attention over the last decade, mainly due to the renewed interest in sustainable ways to produce hydrogen. Although many excellent reviews and book chapters are already available in the literature, the data collected by the authors are organized in a different way, giving more focus to selected types of LOHCs, including inorganic and organic types, type of reactor and classes of compounds. In this way, readers can easily find access to the state-of-the-art data in homogeneous and heterogeneous approaches to hydrogen production from specific classes of LOHCs. I would recommend publication of this review article, however some important points listed below need to be addressed.

1) LOHCs such as formic acid and methanol are generally considered as REVERSIBLE hydrogen sources as they can be re-obtained by CO2 hydrogenation. It is odd to find them listed as irreversible LOHCs. The authors should comment on this and consider the possible addition of citations of examples of reversible charge-discharge processes.

2) In the field of homogeneous catalysis, the number of highly efficient catalysts for selective dehydrogenation of LOHCs is immense, and the authors made choices on specific examples chosen from Ru, Ir, Mn and Co complexes. However, very efficient Fe complexes are known for HCOOH dehydrogenation, and should be included (also in Table 1). In Table 1, some important complexes are missing (see the work of Laurenczy, Beller, Klankermayer and Leitner, for example).

3) I suggest to add a Table with TON and TOF values for the catalytic systems described throughout the main text. This would be very helpful for the readers.

4) In the reference section, all authors names are wrongly cited. The citations should be in the form given name initial. surname. For some reasons, the authors reported the full given name and surname initials. For example, in ref 1, Vincenzo, B.; Nicola, A. should instead be V. Balzani, N. Armaroli. This mistake is repeated for all references and should be corrected.

Author Response

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Reviewer 2 Report

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Round 2

Reviewer 1 Report

The authors have revised the manuscript according to the list of queries. As the manuscript was substancially improved, I recommend publication in the present form.