Synthesis of Hollow Leaf-Shaped Iron-Doped Nickel–Cobalt Layered Double Hydroxides Using Two-Dimensional (2D) Zeolitic Imidazolate Framework Catalyzing Oxygen Evolution Reaction

Round 1

Reviewer 1 Report

In the present work, Quoc Hao Nguyen at al. reported iron-doped nickel–cobalt layered double hydroxides using two-dimensional (2D) zeolitic imidazolate framework catalyzing OER. L-Fe-NiCoLDH showed high OER performance with an overpotential of 243 mV at 10 mA cm−2 and high durability after 20 h. Although there are some minor problems, this manuscript is well structured and fully argued. Therefore, I think this manuscript can be published on catalysts after noticing the following issues:

1. The activity of catalytic sites can directly reflect the catalytic activity. The authors need to measure electrochemical surface area (ECSA) and provide the ECSA corrected polarization curves of the catalysts.

3. However, it is always better to check stability of electrocatalyst at high current density. It is advised to authors to check stability of L-Fe-NiCoLDH electrode at 100 mA/cm2 current density.

3. Given the topic and scope of the paper, some important references should be highlighted to broaden the readership （Interface engineering of the NiCo2O4@MoS2/TM heterostructure to realize the efficient alkaline oxygen evolution reaction, International Journal of Hydrogen Energy, 2023, https://doi.org/10.1016/j.ijhydene.2022.12.184；Catalysts 2022, 12(9):996 DOI: 10.3390/catal12090966; Nanomaterials 2022,12(7):1227;Fuel 2023,332:126227）.

4. HR-TEM of the L-Fe-NiCoLDH sample should be added.

5. Authors should pay attention to the effect of doping on electronic structure and the change of catalyst before and after use.

6. I am interested to see HER performance of electrocatalysts at in alkaline solution. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This work reports the synthesis of leaf-shaped iron-doped nickel-cobalt layered double hydroxides for the oxygen evolution reaction. As the development of novel catalysts for this important reaction is necessary, this work is interesting. However, some issues need to be addressed before the publication:

1.    What is the mechanism that the authors propose for the increase of the surface area from the incorporation of Fe?

2.    The authors also pointed out that the design of nanostructures such as LDHs based on the leaf morphology of MOFs can significantly enhance OER efficiency, but they do not clearly explain why.

3.    On the other hand, they stated that the morphology of L-Fe-NiCoLDH-1 was maintained, however, the morphology of L-Fe-NiCoLDH-3 using high Fe3+ concentration was almost completely broken. So, in this case, what is the precise effect of the morphology?

4.    What does the change in the shape of the hysteresis of the sample L-Fe-NiCoLDH-2 indicate? Does this affect the electrocatalytic activity?

5.    There is a lack of discussion of the XPS results that may show the modification of the electronic structure of these catalysts. A table with the respective binding energy values and the percentage of each oxidation state for Ni, Co, and Fe must be added and discussed.

Therefore, I do not recommend the publication of the manuscript in its present form.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

In the article, the authors tackled a trendy topic in the field of catalysis concerning the synthesis of nickel–cobalt layered double hydroxides. The above subject is very intensively exploited due to the search for the best catalyst for OER. In order to improve the catalytic properties of NiCoLDH, the authors used ideas already known in the literature, e.g., metal-organic frameworks were used as the substrate, and NiCoLDH was treated with iron to improve its catalytic properties.

The catalyst synthesis process has been very well documented and described. The synthesized materials were thoroughly characterized using advanced research techniques, and then the materials underwent a series of electrochemical tests confirming their excellent catalytic properties. Based on the obtained research results, the authors present logical and unambiguous conclusions confirming the effectiveness of the method used to improve the properties of the base material, which is NiCoLDH.

English is understandable. The selection of literature references is correct and refers to the latest achievements in nickel-cobalt layered double hydroxides. In my opinion, the article meets the criteria set out in the requirements of the Catalysts journal and is suitable for publication.

An undoubted weakness of the article is the poorly emphasized topic of novelty, which would distinguish the synthesized materials from many similar ones. Many publications in the literature describe the synthesis and properties of nickel-cobalt layered double hydroxides. An attempt to clearly distinguish the novelty in the Fe-NiCoLDH synthesis process could result in greater interest in the performed research.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report