Effect of Synthesis Conditions on Capacitive Properties of Porous Carbon Derived from Hemp Bast Fiber

Round 1

Reviewer 1 Report

Review Energies

The authors prepared activated carbon from hemp bast fiber, followed by the treatment with HNO3 to introduce N and gas treatment in the airflow. The authors state in the introduction that the heteroatoms and the functional groups introduced into the carbon materials have an important role in energy storage mechanisms. However, in the whole paper, there is not a single analysis of the exact amount of nitrogen introduced (apart from the fact that HNO₃ is not the best precursor to introduce N into carbon) nor the oxygen functionalities that are for sure introduced to the carbons during the 1h treatment in air. Characterization of the prepared carbons' surface chemistry should be added to clarify the conclusions, which are based solely on the carbons' porosity, surface area, and crystallinity.

The introduction lacks a review of published works on biomass-derived carbon materials for energy storage and other applications. There are already a few works dealing with synthesis of carbon from Hemp Bast Fiber  e.g “High-Surface-Area Mesoporous Activated Carbon from Hemp Bast Fiber Using Hydrothermal Processing” or “High-performance solid-state supercapacitor based on sustainable synthesis of meso-macro porous carbon derived from hemp fibres via CO2 activation”, or “HEMP-derived activated carbon fibers by chemical activation with phosphoric acid”. What is the novelty of the work presented in this manuscript in the view of the works already published in this subject.

Line 31- Growth two times in the same sentence

Line 39- “Now the world continues to actively develop new technologies and effective methods for the intensification of oil, gas and 40 coal production [7,8,9], which require reliable equipment [10,11,12,13]-This statement is not valid considering the geopolitical situation in Europe. Given the war in Ukraine and the energy crisis in Europe and around the globe, the efforts are more concentrated on finding sustainable and green replacements for petroleum-based products.

Line 53-clarify the statement “It should be noted that the electrical properties of carbon depend on outside influences, in particular on deformation and magnetic ones? What do authors mean by “influences”? What are “magnetic influences”?

Line 92- for electrical energy storage

Why did the authours used HNO3 to introduce N? It is known that the treatment of carbon with HNO3 introduces mostly oxygen functionalities in the form of carboxylic and carboxylic anhydrides with only traces of nitrogen… The precursors to introduce nitrogen are; melamine or urea or treatment with gaseous ammonia.

Why were the functionalised carbons treated at 400 C in air? The treatment would lead to the introduction of phenolic functionalities to the carbon materials …

Line 205-it should be expected that the SBET increases with the treatment in air at 400 °C, because a large burn-off of carbon should be expected during this treatment. What was the burn-off of this step?

The treatment with acid should decrease the number of micropores and increase the number of mesopores. The treatment with acid normally results in the collapse of micropores and the increase of mesopores. Why is it different in this work (line 217)?

Author Response

Dear Reviewer,
you can find the response in the attached file.
Best regards,
Authors

Author Response File: Author Response.docx

Reviewer 2 Report

After I read this article carefully, I feel that this article lacks scientific significance, lacks research value, and lacks innovation. I'm very sorry, but I don't recommend posting it.

Author Response

Dear Reviewer,
you can find the response in the attached file.
Best regards,
Authors

Author Response File: Author Response.docx

Reviewer 3 Report

1. The authors should explain why the ID/IG ratio increases and what it attributed to
2. Furthermore, the authors should also explain what the significancybof a larger Sbet is and why the type iv hysteresis loop is important in capacitive behavior
3. The authors mentioned that low scan rate have a quasi-rectangular shape, demonstrating the electrostatic mechanism of charge storage. The authors should also add that it demonstrated edlc behavior
4. The authors should explain why there is a hump at 0.4V in figure 5b KN1, what does it signify
5. The authors should know a clear triangular GCD represents dominance of EDLC behavior  ot just capacitive behavior because that can mean EDLC or pseudocapacitive behavior

Author Response

Dear Reviewer,
you can find the responses in the attached file.
Best regards,
Authors

Author Response File: Author Response.docx

Reviewer 4 Report

The authors investigated a porous carbon material with a turbostratic structure obtained from hemp fibres for future use as an electricity storage material. It was investigated how different synthesis and treatment conditions influence the structure, porosity and electrochemical properties, in particular capacitive. The work contains the results of a series of tests subordinated to the optimization of properties and the possibility of controlling carbon material parameters. The possibility of distinguishing between the inflow of the inner (in micropores) and the outer interface to the capacitance of the electrical double layer has been noticed.

The manuscript contains many research results justified by the purpose of the article. The manuscript is written carefully and sparingly, with no unnecessary paragraphs. Only the initial part of the introduction (lines 29 to 46) seems obvious to me nowadays and for the cohesiveness of the whole manuscript, it could be significantly shortened together with some references.

"s" is missing in line 245 (should be: "(6.92+_0.16)10⁻⁶ s", no unit (second) for the relaxation time value)

Author Response

Dear Reviewer,
you can find the response in the attached file.
Best regards,
Authors

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The manuscript was adequately revised. Minor checks of spelling and formatting are required before publishing.

Reviewer 2 Report

It can be accepted.