Fabrication of Platinum-Decorated NiCo-Layered Double Hydroxide Nanoflowers for Electrocatalytic Ammonia Oxidation Reaction
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript present a nice work with all analyses which were done perfectly. I would like to accept this manuscript in the present for but there is a very minor point:
References 1-3, the title of the references were not mentioned like other references.
Author Response
The manuscript present a nice work with all analyses which were done perfectly. I would like to accept this manuscript in the present for but there is a very minor point:
Question 1: References 1-3, the title of the references were not mentioned like other references.
Response: Thanks for this comment.
We are very sorry for this obvious mistake. In this revised manuscript, related information has been added:
[1] Z. H. Lyu, J. J. Fu, T. Tang, J. N. Zhang, J. S. Hu, Design of ammonia oxidation electrocatalysts for efficient direct ammonia fuel cells[J]. EnergyChem, 2023, 5: 1000093.
[2] H. Kim, S. Hong, H. Kim, Y. J. Jun, S. Y. Kim, S. H. Ahn, Recent progress in Pt-based electrocatalysts for ammonia oxidation reaction[J]. Applied Materials Today, 2022, 29: 101640.
[3] D. T. Tran, T. H. Nguyen, H. Jeong, P. K. L. Tran, D. Malhotra, K. U. Jeong, Nam H. Kim, J. H. Lee, Recent engineering advances in nanocatalysts for NH3-to-H2 conversion technologies[J]. Nano Energy, 2022, 94: 106929.
Reviewer 2 Report
Comments and Suggestions for AuthorsAfter adding urea, most likely, precipitation of hydroxides in the form of a suspension began. If so, then it would be more correct to mention that a suspension, not a solution, was placed in the autoclave.
It is unclear why SEM and TEM images as well as XRD are given not for all samples.
Was a comparison made between the different platinum deposition methods in terms of quantitative composition? Was the platinum deposition not electrochemical (was there a blank experiment)?
Author Response
Comments by reviewer (2)
After adding urea, most likely, precipitation of hydroxides in the form of a suspension began. If so, then it would be more correct to mention that a suspension, not a solution, was placed in the autoclave.
Response: Thanks for this comment.
We have revised related sentence in this revised manuscript.
Question 1: It is unclear why SEM and TEM images as well as XRD are given not for all samples.
Response: Thanks for this comment.
In this work, we would like to design one Pt-NiCo-LDH-Ni foam as electrocatalyst for ammonia oxidation reaction. Based on the electrochemical measurements, Pt-NiCo-LDH-Ni foam-3 showed the best electrochemical performances. Therefore, the SEM, TEM and XRD were used to characterize morphology and crystal structure of NiCo-LDH-Ni foam and Pt-NiCo-LDH-Ni foam-3. Actually, based on the SEM images of NiCo-LDH-Ni foam and Pt-NiCo-LDH-Ni foam-3, the morphologies of NiCo-LDH-Ni foam and Pt-NiCo-LDH-Ni foam-3 can be observed. And HRTEM image of Pt-NiCo-LDH-Ni foam-3 can observe the lattice stripe of Pt. Therefore, we did not provide the SEM, TEM images and XRD pattern of all samples.
Question 2: Was a comparison made between the different platinum deposition methods in terms of quantitative composition? Was the platinum deposition not electrochemical (was there a blank experiment)?
Response: Thanks for this comment.
In this work, Pt has been electrodeposited on NiCo-LDH-Ni foam via CV technique with different cycles. Owing to the samples on the Ni foam, it is very difficult to remove under the same condition. Therefore, ICP measurement can not be used to analyze the ratio of Pt in different samples. Based on the electrocatalytic measurements, with the increasing cycles, the electrochemical performances of sample increased, However, when cycles achieved 20, Ni foam has been etched, resulting in decreased electrochemical activity.
In addition, Fig. 4d showed the CV curves of Pt-Ni foam, NiCo-LDH-Ni foam and Pt-NiCo-LDH-Ni foam-3 in 0.1 M NH4Cl. Based on the CV curves, NiCo-LDH-Ni foam can act as the blank experiment to prove the important role of Pt.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsZhao et al. synthesized Pt-decorated NiCo LDH nanoflowers for efficient NH3 oxidation reaction. Electrochemical measurements and characterizations were performed to demonstrate the performance origins. However, following issues should be carefully solved before acceptance.
1. The molecular structure of NiCo LDH should be given for better understanding its structure in Figure 1d.
2. For O 1s XPS, the fitting and analysis are unreasonable. The fitting data cannot match the raw data because they ignore the fitting of other oxygen species, e.g., lattice oxygen and adsorbed oxygen, which should exist for NiCo LDH material. Please re-fit the O 1s XPS and re-analyze the results by referring to the paper with DOI of 10.1039/D1TA10652J.
3. The discussions about the underlying synergetic effects between Pt and NiCo-LDH should be enhanced by providing a schematic plot. The relationships between synergetic effects and NH3 oxidation performance should also be discussed.
4. It is important to identify the products from NH3 oxidation, which is critical for demonstrating the catalysis mechanism. Please refer to this work with DOI of 10.1002/aenm.202401675 for identifying the products from NH3 oxidation.
5. The performance and stability of this material should be compared with other reported materials.
Comments on the Quality of English LanguageMinor editing of English language required.
Author Response
Comments by reviewer (3)
Zhao et al. synthesized Pt-decorated NiCo LDH nanoflowers for efficient NH3 oxidation reaction. Electrochemical measurements and characterizations were performed to demonstrate the performance origins. However, following issues should be carefully solved before acceptance.
Question 1: The molecular structure of NiCo LDH should be given for better understanding its structure in Figure 1d.
Response: Thanks for this comment.
Molecular structure can help us to understand the structure of NiCo-LDH. Unfortunately, though we have tried our best to find and search for CIF documents, we were unable to find the resources. We are very sorry that we cannot provide molecular structure.
Question 2: For O 1s XPS, the fitting and analysis are unreasonable. The fitting data cannot match the raw data because they ignore the fitting of other oxygen species, e.g., lattice oxygen and adsorbed oxygen, which should exist for NiCo LDH material. Please re-fit the O 1s XPS and re-analyze the results by referring to the paper with DOI of 10.1039/D1TA10652J.
Response: Thanks for this comment.
Based on the comment, we have downloaded this paper (DOI: 10.1039/D1TA10652J). This paper reported one BaCe0.16Y0.04Fe0.8O3-б nanocomposite. The XPS of O 1s has been fitted into surface-adsorbed oxygen and lattice oxygen. However, we think this result is unreasonable to transfer to our work. Therefore, we have fitted XPS of O 1s in this work based on some papers about NiCo-LDH as shown in Fig. R1. Some sentences have been added in this revised manuscript: As shown in Fig. 4c, the XPS spectra of O 1s could be fitted into three peaks. The peaks at 531.0 eV, 531.71 eV and 532.62 eV could be attributed to oxygen vacancy, OH- and H2O.
[1] J. He, Z. F. Hu, K. Deng, R. J. Zhao, X. B. Lv, W. Tian, Y. X. Zhang, J. Y. Ji, A triple-layered PPy@NiCo LDH/FeCo2O4 hybrid crystalline structure with high electron conductivity and abundant interfaces for supercapacitors and oxygen evolution[J]. CrystEngComm, 2021, 23: 2262.
[2] C. Y. Zhang, X. Q. Du, X. S. Zhang, Yanhong Wang, Ni3S2/MxSy–NiCo LDH (M = Cu, Fe, V, Ce, Bi) heterostructure nanosheet arrays on Ni foam as high-efficiency electrocatalyst for electrocatalytic overall water splitting and urea splitting[J]. Dalton Translations, 2023, 52: 763.
[3] Y. X. Li, Y. Q. Xu, C. J. Li, W. F. Zhu, W. Chen, Y. F. Zhao, R. Q. Liu, L. J. Wang, ZIF-67-derived NiCo-layered double hydroxide@carbon nanotube Architectures with hollow nanocage structures as enhanced electrocatalysts for ethanol oxidation reaction[J]. 2023, 28: 1173.
Figure R1. O 1s XPS spectra of Pt-NiCo-LDH-3
Question 3: The discussions about the underlying synergetic effects between Pt and NiCo-LDH should be enhanced by providing a schematic plot. The relationships between synergetic effects and NH3 oxidation performance should also be discussed.
Response: Thanks for this comment.
Based on the comment, a scheme of Pt-Ni foam, NiCo-LDH-Ni foam and Pt-NiCo-LDH-Ni foam-3 electrodes for ammonia oxidation reaction has been designed. During the electrochemical process, Pt showed the electrocatalytic acitivity for ammonia oxidation reaction. In addition, NiCo-LDH has been oxidized into NiOOH and CoOOH in 1M KOH. NH3 was oxidized and formed N2 by NiOOH and CoOOH. But, after achieving Pt-NiCo-LDH-Ni foam-3 electrode, the electrocatalytic performances showed further enhancement.
Figure R2. The scheme of the electrocatalytic process of ammonia oxidation reaction on the surface of Pt-NiCo-LDH-3 electrode
Question 4: It is important to identify the products from NH3 oxidation, which is critical for demonstrating the catalysis mechanism. Please refer to this work with DOI of 10.1002/aenm.202401675 for identifying the products from NH3 oxidation.
Response: Thanks for this comment.
The reference of the above-mentioned has been read and this is deep research. On one hand, it is very difficult for us to achieve this level based on our lab condition and revised time. On the other hand, based on the literature on Pt-based catalysts for ammonia oxidation reaction, the products from ammonia oxidation have usually been thought to be N2 based on two famous mechanisms with different intermediates proposed by Oswin/Salomon and Gerischer/Mauerer [H.G. Oswin, M. Salomon, The anodic oxidation of ammonia at platinum black electrodes in aqueous KOH electrolyte, Can. J. Chem. 41 (1963) 1686–1694; H. Gerischer, A. Mauerer, Untersuchungen zur anodischen oxidation von ammoniak an platin-elektroden, J. Electroanal. Chem. Interfacial Electrochem. 25 (1970) 421–433]
Question 5: The performance and stability of this material should be compared with other reported materials.
Response: Thanks for this comment.
Based on the comment, a table has been added in this revised manuscript.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for Authors-
