Grain Boundary—A Route to Enhance Electrocatalytic Activity for Hydrogen Evolution Reaction

Round 1

Reviewer 1 Report

The manuscript submitted by Dong and co-workers describes that hydrogen evolution reaction performance is greatly enhanced by Au grain boundaries, demonstrating by theory and experiments. This work is interesting and important. I recommend this work to publish in Applied Sciences after the revisions. Some specific comments are listed in the following:

1. XRD and SEM should be added.
2. Authors should show the data of electrochemically active surface area (ECSA).
3. How to calculate TOFs? List the equation.

Author Response

Thank you for your consideration and we greatly appreciate all of the comments raised by the referees. The manuscript has been revised thoroughly according to the comments, and all changes have been highlighted by yellow color in the revised manuscript file. In the followings, we list the point-by-point response to the reviewers’ comments, together with a list of changes made.

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript under review is related to the novel, scientifically and technologically valuable analysis of the role of grain boundaries on Au (110) surface in enhance of electrocatalytic activity for hydrogen evolution reactions. The findings that the broken local spatial symmetry near grain boundaries causes the decrease in the coordination numbers of the surface sites and the shift-up of d-band center, thereby reducing the limiting potential for each proton−electron transfer step could be valuable for further research on the novel or improved catalyst for hydrogen evolution reactions. Additionally, the presented research properly combines modeling and experimental activities. That is very positive.

Despite all benefits, the manuscript could be improved following comments:

1. The introduction part related to previous studies on the relationship between grain boundaries and the catalytic activity could be extended (showing what was already done, found and challenges emerged). It would help better understand the novelty and added value of the proposed work.
2. The preparation of Au/CFP electrodes was described in a too generic way. What was the purity of Au used for the deposition? Modes of magnetron sputtering used (RF?, DC?, Pulsed DC? etc.)? The sentence “The use of an air atmosphere prevented the formation of carbon coatings on the Au nanoparticles” is not so clear. Additional clarification would be helpful.
3. Did you observe any changes in elemental composition or formation of new compounds (any signs, for example, of oxidation?) after annealing in flowing air at 100 sccm heated at temperatures (200 ~ 400 °C) for 2 hours? Additional XPS measurements could confirm that the surface composition remains the same (for no oxidation, changes in the presence of functional groups on the very surface, etc.) after annealing, and all effects are mainly due to change in GBs density.
4. Annealing of Au/CFP electrodes is described in a confusing way. If to look line 95 “…with flowing air at 100 sccm heated at a given temperature (200 ~ 400 °C) for 2 hours.”. However in lines 239-241: “… we annealed the pristine Au/CFP under Ar atmosphere at different temperatures such as 300 °C and 400 (denoted as Au/CFP300 and Au Au/CFP400).”. Which description of annealing procedures are true?
5. There are light yellow lines in Fig.5 which indicate GBs in as-deposited sample and sample annealed at 300 C. What about white lines for annealed samples? Is it lattice fringe spacing for Au NPs? Is it possible to point out the exact spacing in nm?
6. There are some typos, such as in lines 137, 374 “HRE” (should be “HER”?);

Author Response

Thank you for your consideration and we greatly appreciate all of the comments raised by the referees. The manuscript has been revised thoroughly according to the comments, and all changes have been highlighted by yellow color in the revised manuscript file. In the followings, we list the point-by-point response to the reviewers’ comments, together with a list of changes made.

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The manuscript is properly improved following the reviewer's comments.