Pivotal Role of Ni/ZrO₂ Phase Boundaries for Coke-Resistant Methane Dry Reforming Catalysts

Round 1

Reviewer 1 Report

The authors compared an “inverse” near-surface intermetallic NiZr catalyst precursor with the respective bulk-intermetallic NixZry material and a supported Ni-ZrO2 catalyst. The performance for the methane dry reforming was studied. There are some questions need to be addressed. 

1. The impregnated “Ni10Zr90” supported powder catalyst was prepared with a Ni:Zr ratio of 10:90, while the other catalyst was prepared by resistive heating of a stack of alternating small pieces of clean Ni foil possess a nominal ratio of Ni:Zr of 80:20, what’s the reason for the selection of the Ni:Zr atomic ratios?

2. For the Zr3d XPS spectra in Fig. 1 and Fig. 5, the numbers of the fitted peaks are not consistent, some are two, some are four, some are six, is there any criterion for the fitting work?

3. How about the structure comparsion for the different catalysts? Does the structure affect the performance of methane dry reforming?

4. For the activity test in Fig. 3 and Fig. 4, what’s the size of the catalyst particles? does the catalyst need to be crushed before the test?

5. For the SEM images in Fig. 8, how was the Ni and ZrO2 were confirmed

6. Is there any carbon deposited for the spent catalyst?

7. The references should be uniformed, such as the abbreviation and the capitalization of the first letter.

Author Response

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Reviewer 2 Report

Ni-oxide interface is kind of the common sense in the field to understand the decoking of methane dry reforming reaction. The article provides the three Ni-ZrO2 catalysts with different Ni:Zr ratios as well as the preparation methods. I don't see the conclusion can be supported by any of the evidence authors provide, and the I don't see any novelty from their conjected mechanism. There are also the low-quality SEM images and an avalanche of results reproduced from the publication already exists. I would suggest the editor to reject the paper.

Author Response

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Reviewer 3 Report

The contribution of Leander Haug and colleagues represents a deep insight into the action of Ni-ZrO₂ dry methane reforming catalysts and, more specifically, the role of ZrO₂ in the reaction mechanism and cocking formation. The work is interesting and well written, the conclusions are reasonable. I see no flaws in the manuscript and recommend it for publication as is.

 

The main topic of the presented studies is how ZrO₂ contributes to the DRM reaction mechanism and Ni resistance to deactivation via cocking.
I believe that the authors’ approach is original and the results obtained are important for fundamental understanding of DRM Ni catalysts action.
Authors prepared and tested ‘traditional’ supported and bulk Ni-ZrO₂ catalysts as well as ‘inverse’ (ZrO₂ supported on Ni foil) catalyst for comparison. They were studied by ex- and in situ XPS, SEM and EDX methods. This original approach makes it possible to elucidate the metal-oxide boundary contribution to the coking resilience of the catalysts studied.

Authors applied here a rather sophisticated UHV setup for in situ spectroscopic characterization of their catalysts. This equipment is described in detail in the article cited (Ref. [40]).

I believe that the conclusions is consistent with the results obtained and provide relevant summary of the article.

The citing of previous reports is relevant and sufficient.

There are no tables in the manuscript. The pictures are good enough for me. Possibly, higher resolution images and more contrast inscriptions in the pictures may be desirable.

Author Response

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Round 2

Reviewer 2 Report

Comments for author File: Comments.pdf

Author Response

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