Gas Barrier Performance of Hexagonal Boron Nitride Monolayers Grown on Copper Foils with Electrochemical Polishing

Round 1

Reviewer 1 Report

The manuscript tries to describe the synthesis of hexagonal boron nitride (h-BN) on electrochemically polished copper foils and investigated the gas barrier performance of the as-prepared h-BN monolayer. The authors used various techniques such as SEM, Raman spectroscopy, XPS, etc., to verify the growth of h-BN monolayers on the foils. Then tested the water vapor transmission rate (WVTR) and water vapor permeability of h-BN monolayers. The title and abstract are appropriate for the content of the text. However, the background/literature review on this topic is not sufficient, the experimental section lacks the details of materials used, and data analysis needs improvement.   

Strengths: The authors used a cost-effective strategy and green chemistry routes to synthesize the h-BN. The paper is built on the group’s previous findings (ref.7).

Weakness:

• Overall, the manuscript is poorly written. Sentences were constructed poorly. For instance, in lines 78 – 81 “… ECP was conducted in a solution with phosphoric acid and water at 1.8 V for 10 min….” – does not clearly describe the information in Fig S1 – the information is not consistent. In lines 83 – 84, the term “Nippon Mining” is not clear whether the authors try to describe the synthesis process or the source of copper foils.
• The authors failed to present the detailed sources of materials and equipment used for the experiment under the “Methods” section.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

Review of Manuscript applsci-1204048: Gas barrier performance of hexagonal boron nitride monolayers grown on copper foils with electrochemical polishing

The work by Lee and coworkers investigates the gas barrier performance of h-BN monolayers deposited on copper foils. First, the authors characterize the films deposited with and without electrochemical polishing (ECP), demonstrating that the crystallinity of the monolayer is highly enhanced by ECP (i.e., the density of defects is reduced). Second, they show that the higher crystallinity enhances its performances as a gas barrier, reducing the water vapor transmission rate.

The manuscript is well written, the analyses are robust and the results clear. I have just a couple of doubts.

1) In the cited reference 9, it is said that graphene shows indeed great performances in the first few hours after deposition, but these performances are easily deteriorated on longer time scale. In fact, they show that after years graphene even comes to be detrimental as a gas barrier, favoring instead of preventing oxidation.

Do the authors believe that h-BN would behave differently over long time scales? I personally think that there are reasons to think so, especially because of the wide band gap, as it is correctly highlighted by the authors, but an additional comment would make the point more clearly stated.

2) WVTR without ECP is 798 gm^-2 day^-1, while with ECP is 764 gm^-2 day^-1. The difference looks little, especially when compared to bare PET. What is the practical difference of this difference in terms of the substrate material durability?

A comment about this would make the point stronger as well.

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.docx