On a Composite Obtained by Thermolysis of Cu-Doped Glycine

Round 1

Reviewer 1 Report

The work “On a Composite Obtained by Thermolysis of Cu-doped Glycine” reports a method for producing a composite material with high conductivity and shielding ability for THz radiation.

The composite material was obtained on the basis of glycine and copper acetate monohydrate under exposure to temperatures from 400 to 550 °C. A detailed study of its structure was carried out using scanning and transmission electron microscopy, multi-element analysis using energy-dispersive X-ray spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, infrared and Raman spectroscopy and UV spectroscopy. As a result, a sample with a conductivity value exceeding the corresponding value for the glycine thermolysis product was obtained. Such a carbon matrix composite with a 6:1 mixture of graphene carbon and an N-ring copper chelate resembling diazetidinedione (C₂H₂N₂O₂) that is electrically conductive could find applications in electronics and energy storage. Doping with copper led to an increase in the absorption of THz radiation, and based on the achieved values, it can be concluded that shielding from THz radiation is possible. The use of such radiation is important for the development and implementation of new technologies.

There are some points in the work that require corrections and additions:

1.                 It is not clear how to correctly perceive Figure 1. There are two drawings, but they don’t look like the same sample from different angles. It is necessary to add an explanation of parts of the drawing or provide images for different samples.

2.                 The text does not provide a description of the symbols used in formula 1

3.                 The description of the THz absorption study is not sufficiently presented. It is necessary to add a description of the experimental setup used or references to the literature with a detailed description.

4.                 The work presents the results of studies when exposed to temperatures from 400 to 550 ºС. At the same time, the “Discussion” section provides data on the effects of temperatures from 200 to 400 ºС. It is necessary to provide references to relevant literature, lines 430-435.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

"X-Ray Powder Diffraction Characterization" section is too short. Additional information can be derived from obtained data, without the need for new measurements:

Line 317-317 and 322-323. Please provide the calculated interplanar value (d) for the broad peak associated with graphite. How does it compare to the value calculated from STEM images (Line 213-214)?

Line 316. Since metallic Cu has cubic unit cell, it is possible to calculate the lattice cell parameter a using the position of single diffraction peak, (111) or (200). How does this compare to the reference data for Cu metal?

Using the Scherrer formula it is also possible to estimate the coherent scattering region sizes for Cu, CuO and Cu2O. These values can also be compared to the SEM data. All of the measurements described above are fairly easy to perform and provide useful information about the sample structure.

Rietveld analysis could also be performed in order to estimate the Cu/CuO/Cu2O proportion, however it is significantly harder to perform correctly, so I don't insist on its implementation.

Lines 170-171 "X-ray powder diffractograms (XRPD) were obtained using a Bruker D8 DISCOVER A25 diffractometer in reflection mode". Does this refer to the Bragg-Brentano geometry?

Line 173 "crystalline silicon served as a standard " Please elaborate further what kind of silicon material was used as reference standard - ordinary polycrystalline silicon powder, SRM 640 silicon powder or perhaps the single-crystal silicon wafer?

Line 314 "Dharacterization" - a typo.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

-Authors need to include the name of the analytical technologies and corresponding abbreviations. For example, for UV-Vis, what is the name of the analytical technique? and for scanning and transmission electron microscopy, what is the abbreviation? 

-Authors need to improve the state of the art about carbonization/pyrolysis or behaviour of glycine

-What is the main application of copper-carbon composites? Authors need to perform a wide review of these uses. Introduction needs to be improved. Characterization of carbon composites needs to be related to its potential uses. 

-Additionally, the main objective of the research needs to be included at the end of the Introduction.

-Authors need to perform a wide description of thermal conditions used. It is perform with N2 or air atmosphere? 

-Why authors used the term "thermolysates"? 

-Authors must do a major revision of their work. The characterization has only been done on some samples, why? Furthermore, the discussion should be improved including references to other articles that help to jystify the obtained results. Additionally, they should aslo improve the quality of the Figures and named the samples. 

Abstract,

-The result "The carbonaceous matrix exhibited a 6:1 ratio of graphitic carbon to a carbon-30 nitrogen compound with the formula C2H2N2O2, such as isomers of diazetidinedione" is obtained by XRD? How much N is in the sample comparing to C? 

-Line 43: Authors said that "Since 2011, research on composites featuring a carbonaceous matrix and copper as a 43 reinforcing element has garnered significant attention.". Why since 2011? I consider that before 2011 these composites were also important. If there is a reason why the authors identify the year 2011, authors should cite it. 

-I consider that the name of the prepared carbon materials is not exactly "glycine-based copper doped composites". Glycine decomposes with heat treatment, glycine is only the raw material used

-Authors need to improve the state of the art about carbonization/pyrolysis or behaviour of glycineç

-What is the main application of copper-carbon composites? Authors need to perform a wide review of these uses. Introduction needs to be improved. Characterization of carbon composites needs to be related to its potential uses. 

-Lines 103-106: Ratios of Cu in the initial mixture is lower than 3wt%. How many Cu is in the final? it can be classified as composite? 

-Line 109. The blue colour is not for glycine, is due to glycine-Cu complex

-Section 2.1. "Synthesis": Authors need to perform a wide description of thermal conditions used. It is perform with N2 or air atmosphere? 

-Lines 120-125: The yields of the process, should be included in a Table in the Results and Discussion Section

-Lines 215: Why authors used the term "thermolysates"? Authors need to homogenize the names of samples and processes along the document. 

-Table 2: Authors need to perform elemental analysis of samples, the content of C, N, H and O should be calculated by elemental analysis and not from EDS

-During description of Figure 5, authors said that exist as Cu metallic form, why? 

-Line 280: Ratios C/N or O/C should be calculated as atomic ratios. Additionally, the calculation of H content is necessary in order to calculate the H/C ratio and the degree of aromatization. 

-Table 8: authors included only 2 samples with Cu at 500ºC, why not with other ratios or temperatures? Additionally, there are C-H groups. However, H content is not included in the elemental analysis content. There are inconsistencies

-Figure 11. The name of samples analysed shoudl be included and should be the same along the document. In each figure authors used different names for samples. Why authors characterized different samples to that characterized by FTIR? 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

This paper investigates the synthesis, characterization, and application potential of a novel composite material composed of a carbonaceous matrix doped with copper, generated through the thermolysis of glycine in the presence of copper acetate. The material's comprehensive characterization employs a variety of analytical techniques, highlighting its unique electrical and terahertz absorption properties, which suggest applications in electronics, energy storage, and terahertz radiation shielding. But the XRD part need more clarification.

Line 323-325, please give more technical details about running Rietveld refinement. And please list each component's wt.% for an apple-to-apple comparison. 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Dear Authors

I consider that characterization is not performed with more adequate techniques. Additionally, for the characterization of carbonaceous samples it is necessary the use elemental analysis (C, H, O, ash) and ratios H/C or O/C. The aromatization degree has a great influence on the electrical properties of materials

I have an important question. How is possible to prepare a carbon material in air atmosphere? At 500ºC more of carbon sample is burned. 

Analysis content of C, H, O or N should be performed by elemental analysis and not by EDS

 

 

Authors do not used the more adequate characterization techniques. For example:

Line 247. Authors said "A TEM micrograph in Figure 2 (left)a displays the particle size of the composite, measuring 350 nm". Particle size analysis should be performed by other technology.

Additionally, content of C, H, O or N should be performed by elemental analysis. 

H/C ratio is related to aromatization and to electrical properties of carbon. So, contrary to oppinion of authors, it is necessary to perform analysis. 

 

Author Response

Major comments

Dear Authors

Q1. I consider that characterization is not performed with more adequate techniques. Additionally, for the characterization of carbonaceous samples it is necessary the use elemental analysis (C, H, O, ash) and ratios H/C or O/C. The aromatization degree has a great influence on the electrical properties of materials

Response: The reviewer's concerns regarding the characterization techniques employed have been addressed. CHNS elemental analysis has been performed and reported. Subsection 2.2 has been updated to include details on the equipment utilized for the elemental analysis. Furthermore, a new subsection (3.5) has been incorporated to present the comprehensive elemental analysis results, along with the C/N, C/O, and C/H ratios.

Q2. I have an important question. How is possible to prepare a carbon material in air atmosphere? At 500ºC more of carbon sample is burned.

Response: The reviewer raises a concern regarding the possibility of carbon material combustion when the thermolysis process is carried out in an air atmosphere at 500 °C. However, as noted in the previous revision round (refer to Q5), the thermolysis process was conducted under static air conditions, utilizing a crucible with a lid.  Under static air conditions, the amount of oxygen available for reaction with the carbon material is limited due to the semi-closed system created by the lidded crucible. This restricted oxygen supply mitigates the risk of complete combustion of the carbon material, even at elevated temperatures such as 500 °C. While an air atmosphere may lead to combustion under unrestricted conditions, conducting the process under static air with a limited oxygen supply allows for the formation of the desired carbon material without complete oxidation.

Q3. Analysis content of C, H, O or N should be performed by elemental analysis and not by EDS

Response: Please refer to the response to Q1.

Detail comments

Authors do not used the more adequate characterization techniques. For example:

Q4. Line 247. Authors said "A TEM micrograph in Figure 2 (left)a displays the particle size of the composite, measuring 350 nm". Particle size analysis should be performed by other technology.

Response: The sentence has been revised as follows: "A TEM micrograph of the composite is displayed in Figure 2a. [...]". Details regarding particle size have been omitted. Given that no statements are made regarding composite particle size, the requested particle size analysis, which is beyond the study's scope, is no longer necessary.

Q5. Additionally, content of C, H, O or N should be performed by elemental analysis.

Response: Please refer to the response to Q1.

Q6. H/C ratio is related to aromatization and to electrical properties of carbon. So, contrary to oppinion of authors, it is necessary to perform analysis.

Response: Please refer to the response to Q1.

Round 3

Reviewer 3 Report

Dear authors, 

Sorry but I recommend to perform a wide review and study of data. I have rejected two times the manuscript. Please, review it carefully. 

Dear authors, 

I consider that it is basic for researches in the area of carbon materials to understand the elemental analysis of samples and specially, the calculation of atomic ratios H/C and its evolution with carbonisation. I have rejected two times the manuscript for mistakes in the characterization. You have included a new paragrapht 3.5, but the H/C ratios of pristine and carbon material is different (you calculate C/H). You only said that it is not substantial!!! So, there are not difference in the structure of glycine and carbon material???? How you explain differences of data in Table 3?  there should be no incongruences along manuscript!.

You calculate the Cu content by EDS??? The ash content should be calculated by the combustion process!!!

Authors said that "the  aim of the study is to provide a comprehensive characterization of the pyrolysis products through a diverse range of techniques, along with electrical conductivity and radiation absorption in the terahertz band measurements. This broader scope aims to explore additional potential applications for this new material." How many products? there are analysis performed by several products and other analysis only for one. And high important, the authors must perform analyses and calculations correctly!!!

 

Author Response

Please find our responses to Reviewer #3's comments in the pdf file.

Author Response File: Author Response.pdf