Electronic Structure Regulation Enhances the Urea Oxidation Reaction Performance of the NiCo-MOF Catalyst

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

An interesting study based on facile synthesis of NiM-MOF catalysts, and followed with comprehensive electrocatalytic study regarding EOR, UOR, HER and complete water splitting reactions. However, the following points require more clarifications to make the conclusion exclusive.

1. Page 5 line 32, the author mentioned XRD peak intensities difference is related to different synergistic effects between Ni and various doping elements, may you explain more on this? Raw intensity may be impacted by sample loading amount, crystalline size, XRD experiment conditions.
2. Figure 4b shows interesting Ni XPS peak shifting for NiCo-MOF, do you have a control Ni-MOF for comparison?
3. In Figure 4c, why is C-N intensity quite different among the samples?
4. In Figure 8c, the EIS data doesn’t match with the explanation on page 12 line 14.
5. Page 5 line 12, missing space between “where” and “η”.
6. Page 6 line 7, “uniform distribution of Ni, Co, O, and C elements on the material surface”, where Figure 3c missing O mapping data.
7. In Figure 5b and Figure 8c, axis label is cut off, which could be due to format issues.
8. Figure 2c has clearly different scale than 2a, 2b and 2d, it will be better to compare under same magnification.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 2 Report

Comments and Suggestions for Authors

Reviewer Comments

This study reports the synthesis of NiM (M = Co, Mn, W, Zn)–MOF catalysts with nanosheet-assembled spherical morphologies grown in situ on nickel foam and identifies NiCo-MOF (Ni:Co = 1:2) as the most active composition. The catalyst demonstrates superior UOR and HER performance attributed to synergistic bimetallic effects, enabling efficient urea-assisted water electrolysis at low operating voltages with potential for sustainable hydrogen production. Overall, the paper is well written and provides comprehensive characterization results to support its claims. However, a few comments are provided below to improve the quality and scientific contribution of the work.

 Major comments

1. Provide a comprehensive discussion on how surface area (BET) and electronic conductivity (EIS) influence the UOR activity trends (overpotential and Tafel slope) of the Ni-M sample.

2. Revise the SEM description: The morphology appears needle-like rather than nanosheet-like; please update accordingly.

1. Identify and discuss the impurity phases associated with the extra XRD peaks observed for Ni-M (M = Co, Mn, Zn, W) samples in Figure 1b.
2. Explain why there is no significant difference in overpotential among Ni-M (M = Co, Mn, Zn, W) samples for UOR at 10 mA cm-2 as seen in Figure 6f.
3. Compare the UOR and HER results of your catalysts with previous reports on Ni-based MOF catalysts and present this in a table.

 Minor comments

1. Define the chemical DHBA used in the synthesis as shown in Figure 1.
2. Spell-check the manuscript; for instance, "hydromental" in Figure 1a should be "solvothermal" (since DMF is extensively used as the solvent).
3. Simplify the caption for Figure 5.
4. Correct the punctuation in “NiM（M = Co、Mn、W、Zn)-MOF”.
5. Add the equivalent circuit diagram for the EIS results shown in Figures 6d and 8c. Also, include the missing Tafel slope value for NiZn-MOF in Figure 6c.
6. Add the missing Y-axis label in Figure 8b.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents a systematic study on a series of NiM (M = Co, Mn, W, Zn)-MOF electrocatalysts, hydrothermally synthesized on nickel foam, for efficient urea oxidation reaction (UOR) and overall water splitting. Among them, NiCo-MOF with a Ni:Co ratio of 1:2 exhibits the best bifunctional performance, delivering low overpotentials for both UOR and HER. The study combines multiple characterization techniques (XRD, SEM, TEM, XPS, N₂ adsorption, EIS, LSV) to analyze morphology, electronic structure, and electrochemical activity, attributing the enhanced performance to optimized electron transfer and abundant active sites via Co incorporation. While the manuscript is well-organized and addresses a relevant topic in sustainable energy catalysis, several issues must be addressed before the work can be considered for publication in Nanoenergy Advances.

Missing Faradaic Efficiency.

he authors state the formation of NiOOH as active sites, but no clear evidence is shown. Please include post-UOR XRD/XPS/SEM of NiCo-MOF to support this.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The comments of the reviewers' have been well addressed in the manuscript, and it may be accepted for publication in its current form.