Preparation of Porous Ni-W Alloys Electrodeposited by Dynamic Hydrogen Bubble Template and Their Alkaline HER Properties

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Please find attached the review comments

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Author Response

Reviewer 1

 Su et al. studied the electrodeposition of porous Ni-W alloy catalysts from a pyrophosphate bath using the dynamic hydrogen bubble template (DHBT) method. They identified applied current density as a critical factor in forming porous structures, with the concentration of sodium tungstate allowing fine adjustments to pore size and density. The resulting porous Ni-W alloy demonstrated greater alkaline electrochemical hydrogen evolution (HER) performance. In contrast, a cracked Ni-W alloy catalyst, despite having a higher W content, exhibited poor activity. This manuscript is providing relevant insights about the preparation and Alkaline HER Properties of Porous Ni-W Alloys via Dynamic Hydrogen Bubble Template by conducting many characterization techniques and electrocatalytic activities. However, I believe that the present manuscript requires minor revisions for publication in Coatings’ Journal and needs further improvement. Below are my comments:

 

• In the abstract the name of Ni-W alloy should be reported as nickel-tungsten (Ni-W).

Respond: Thank you for your suggestion. In the abstract, we have modified the first Ni-W alloy to nickel-tungsten (Ni-W).

 

• In the abstract, the selection of Ni-W is not explained, e.g.: Ni-W alloys are gaining significant attention as an efficient alternative to hard chromium coatings due to their superior hardness, wear resistance, and corrosion properties, among many.

Respond: According to your suggestion, we have added the explanation about Ni-W alloy in the abstract. Thank you.

 

• Many typo mistakes in the abstract and in the whole manuscript. To be revised intensively.

Respond：We have carefully improved the English of the revised manuscript.

 

• In the abstract the meaning should be reported as RHE (reversible hydrogen electrode). Respond：According to your suggestion, the RHE has been revised to RHE (reversible hydrogen electrode). Thank you.

 

• Figure 2 is not clear, what is the main difference between 3 presented colors. A legend is required to explain the bar chart of Figure 2.

Respond: The three different colors in Figure 2 represent the current efficiency under the same Na₂WO₄·2H₂O concentration of 0.1, 0.3 and 0.6 A cm^-2 current density, respectively. Compared with Figure 2 (a) and (b), in general, the high concentration of Na₂WO₄·2H₂O has a lower current efficiency, so the more hydrogen bubbles are generated and the more advantageous it is for forming porous Ni-W alloys. The explanation about better porous structure (Fig.3) obtained in the bath with high concentration of Na₂WO₄·2H₂O is that hydrogen evolution is the main process. Therefore, we adjusted the order Fig. 2 and Fig. 3, as well as, we changed the bar chart of Fig.2 to line chart in order to understand the phenomenon.

 

6) For XPS analysis, it is good to represent the ratio Ni/W, to check whether you have nickel or tungsten enrichment. Therefore, you can link this to the HER activity whether; a) Nickel is a well-known catalyst for HER, possessing excellent catalytic properties that facilitate the efficient generation of hydrogen. Enriching the catalyst with nickel enhances the surface area available for the reaction, improving overall activity or b) In Ni-W alloys, tungsten enrichment can create synergistic effects with nickel, enhancing overall catalytic performance beyond what each element could achieve individually or c) In Ni-W alloys, nickel simply can create synergistic effects with tungsten, further enhancing the catalytic efficiency and stability of the material.

Respond：This is an excellent suggestion, our analysis of XPS is mainly about the chemical state of the material, XPS can also reflect the Ni/W ratios on the surface, which is comparative with that of EDX data. The synergistic effect of nickel and tungsten is a reasonable explanation about the improvement of HER property of Ni-W alloy versus Ni and W metals. The corresponding analysis has been given in the 3.2 segment. Thank you very much.

 

 

7) I am not expert in EIS but I believe that EIS procedure shall should be more elaborated (at what temperature the EIS has been done; is it at 55°C?). In Figure 10, the Nyquist plots were represented for different catalyst, I would suggest calculating the values of resistivity and thus the conductivity of the material if the results have been done at different temperature using the following relationships:

Response: The electrochemical impedance spectroscopy (EIS) measurements were conducted at room temperature, which had been added in the 2.3 segment. The qualitative analysis of charge transfer resistance (Rct) was performed based on the size of the geometric semicircle in Figure 9, while a further quantitative comparison of Rct values for different materials was carried out in Table 4, Thank you.

Overall, this manuscript, after addressing these minor revisions, holds promise for publication in Coatings' Journal, offering insights for further research in enhancing HER performance through alloy design and electrodeposition techniques.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Comments: Authors report the preparation of porous Ni-W alloys electrodeposited by dynamic hydrogen bubble template and their alkaline HER properties. The structure of the synthesized materials has been characterized well, and these analyses are reasonable. However, the author should revise the review article based on the comments.

1.    The author needs to check the Title of the manuscript. There are typo errors in it, so revise it.   

2.    The abstract needs to be improved with some numerical results drawn from the study to attract the reader's attention. Moreover, the abstract must reflect the whole work. Hence, the author needs to revise the abstract appropriately.

3.    What are all the mechanisms involved in electrodeposition while using a hydrogen bubble template? The detailed mechanisms must be included in the revised manuscript for readers to understand it clearly.

4.    The EDX spectrum of Ni-W alloys needs to be supplied to determine their elemental composition.

5.    What about the surface area of the prepared porous alloy materials?

6.    The author needs to elaborate on the HER performance of the manuscript and correlate current results with literature data.

7.    There are some grammatical errors in the manuscript which have to be rectified for clear understanding.

Comments on the Quality of English Language

The author needs to check minor spell check.

Author Response

Reviewer 2

Comments: Authors report the preparation of porous Ni-W alloys electrodeposited by dynamic hydrogen bubble template and their alkaline HER properties. The structure of the synthesized materials has been characterized well, and these analyses are reasonable. However, the author should revise the review article based on the comments.

1. The author needs to check the Title of the manuscript. There are typo errors in it, so revise it.

Respond：G Minor errors in the title of the manuscript have been revising and the abstract and the manuscript have been checked accordingly.

2. The abstract needs to be improved with some numerical results drawn from the study to attract the reader's attention. Moreover, the abstract must reflect the whole work. Hence, the author needs to revise the abstract appropriately.

Respond：Thank you for your suggestion. The abstract was rewritten and shown in the revised manuscript.

3. What are all the mechanisms involved in electrodeposition while using a hydrogen bubble template? The detailed mechanisms must be included in the revised manuscript for readers to understand it clearly.

Respond：The reviewer is appreciated for the professional comment. The creation of bubbles on the surface of an electrode involves three steps: nucleation, growth and detachment. When hydrogen dissolved in solution comes into contact with the electrode surface, nucleation and growth begin, and during the growth process the contact angle gradually decreases until detachment. At each hydrogen bubble nucleation site, a portion of the gas remains after the bubble is detached, allowing the next bubble to continue to evolve and grow in situ.

In the process of generating bubbles, due to gas insulation, so the Ni-W alloy along the bubble around the growth, with the growth of bubbles, its radius gradually increased so that the formation of the V-shaped profile shown in Figure 4 (b).

 

4. The EDX spectrum of Ni-W alloys needs to be supplied to determine their elemental composition.

Respond：Thank you for your suggestion, as illustrated in Figure 5, the EDX analysis of the Ni-W alloy elements and their specific composition reveals the distinct peak intensity and spacing of Ni and W. However, the O, C, and P peaks are too small and too close together in the figure, making it challenging to identify and distinguish them individually, here are the data I provided:

CNiW10-1

Spectrum 2 Element Wt% Wt% Sigma Atomic % Ni 69.49 0.71 87.70 W 30.51 0.71 12.30 Total: 100.00   100.00

 

 

 

 

 

 

PNiW5-6

Spectrum 17 Element Wt% Wt% Sigma Atomic % Ni 85.55 0.73 94.88 W 14.45 0.73 5.12 Total: 100.00   100.00

 

PNiW10-6

Spectrum 9 Element Wt% Wt% Sigma Atomic % Ni 74.05 0.63 89.94 W 25.95 0.63 10.06 Total: 100.00   100.00

 

 

5. What about the surface area of the prepared porous alloy materials?

Respond: The electrochemical surface-active area (ECSA) has been calculated in Fig. 9, but since there is no instrument in our group to measure the specific surface area, the data in this area.

 

 

 

6. The author needs to elaborate on the HER performance of the manuscript and correlate current results with literature data.

Catalysts material	Overpotential of current density at 10mA cm-2 (mV)	Tafel slope (mV per decade)	pH	Refs.
T-Ru/a-Cu	49	46.4	14	6
Ni-Co	197	92	14	11
Ni-Co	107	118	14	12
Ni-Mo	62(200mA cm-2 and 80oC)	20.1	14.8	14
Ni-Mo	47 (100mA cm-2)	NA	14	15
Ni-W	169	130	14	17
Ni-Co-Mo	132	108	14	20
Ni-Co-Sn	NA	122	14	21
Ni-Cu-Mn	63	111	14	32

 

Respond：This is a professional question, We use the dynamic hydrogen bubble template method to have lower current efficiency and more micropores by regulating its electrochemical deposition reaction, The electrochemical active area was increased and the current density of 10 mA cm^-2 at 166 mV (η10) vs. RHE (reversible hydrogen electrode) was compared with current in reference 17 density of 10 mA cm^-2 at169mV vs. RHE (reversible hydrogen electrode) has a slightly lower overpotential and is completed in one step by electrochemical deposition, which is first electrochemical deposition and then etching, which has the advantages of simpler operation process and rapid preparation.

 

 

7. There are some grammatical errors in the manuscript which have to be rectified for clear understanding.

Respond：Thank you for your advice, I would to manuscript some grammatical errors in the corresponding modification.

 

 

And, other revisions are given using red words in the revised manuscript.  

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have moderately addressed the issues raised by the reviewers. Hence, the revised version of the manuscript may acceptable to the journal standard.