REVIEWER

No.

REVIEWER COMMENT

Corrections of Reviewer Comments

Reviewer No. (1)

English language and style

(x) Moderate English changes required

a. Does the introduction provide sufficient background and include all relevant references?

Yes.

b. Are all the cited references relevant to the research?

Yes.

c. Is the research design appropriate?

Yes.

d. Are the methods adequately described?

YES.

e. Are the results clearly presented?

YES.

f. Are the conclusions supported by the results?

YES.

·   The English language changes are shown in GREEN color according to the Reviewer comment.

a. Thanks for the Reviewer comment.

b. Thanks for the Reviewer comment.

·   c. Thanks to the Reviewer comment.

·   d. Thanks to the Reviewer comment.

·   e. Thanks to the Reviewer comment.

·   f. Thanks to the Reviewer comment.

Comments and Suggestions for Authors

As the authors have addressed most of the comments from the reviewers, the manuscript can be accepted in its present form.

Tanks for the Reviewer comment.

REVIEWER

No.

REVIEWER COMMENT

Corrections of Reviewer Comments

Reviewer No. (2)

English language and style

(x) English language and style are fine/minor spell check required.

·   The English language check are shown in GREEN color according to the Reviewer comment.

Comments and Suggestions for Authors

The authors have revised their paper according to the review comments and the paper can be accepted.

·    Thanks for the Reviewer comment.

REVIEWER

No.

REVIEWER COMMENT

Corrections of Reviewer Comments

Reviewer No. (3)

English language and style

(x) Extensive editing of English language and style required

a. Does the introduction provide sufficient background and include all relevant references?

Must be improved.

b. Are all the cited references relevant to the research?

X Must be improved.

c. Is the research design appropriate?

Must be improved.

d. Are the methods adequately described?

Must be improved.

e. Are the results clearly presented?

YES.

f. Are the conclusions supported by the results?

YES.

·   The English language and style are extensively edited, the changes are shown in GREEN Color.

·   a. The introduction improved to provide sufficient background with 17 References added, and the changes are written in GREEN Color.

·   b. The References are improved to be relevant to the research, the changes are written in GREEN Color.

·   c. The research design be appropriate, and the changes are written in GREEN Color.

·   d. The methods improved to be adequately described, the changes are written in GREEN Color.

·   e. Thanks for the Reviewer comment.

f. Thanks for the Reviewer comment

Comments and Suggestions for Authors

(a) The manuscript is written in a messy way. Many paraghraphs contain numerous style errors and typing errors. Some parts of the text are not clear in meaning. All of them must be re-phrased to clearly indicate the intension of the Authors.

(b) ABSTRACT “As the test temperature increases, the crystallinity index (Ic) of CuO, 1.0MrGO/CuO and rGO are , 90.61%, 88.42% and 86.25% respectively at 500oC and one hr, while it was; 76.30%, 73.51% and 67.77 respectively at 500oC and 30 hrs. Ic% of both rGO and1.0MrGO/CuO increases and that of CuO decreases with test temperature increment, while Ic for both of them decreases with test period increment.”

(b) Thanks for the Reviewer comment, the sentences are corrected according to the Reviewer Comment in GREEN color.

(c) INTRODUCTION is also messy. Many references are mentioned, but the reader does not feel what is the aim of the introduction. If the Authors want present the use of copper in supercapacitors or plant derivatives, they should limit the references to that topics.

(c) (c) The INTRODUCTION is corrected in GREEN color.

·  Many References are added according to previous Reviewers comments in RED and Blue colors.

·  The use of copper in supercapicitors or plant derivatives are added according the First Previous Reviewer comment No. (2) which as follows;” The introduction part is not well written. The current study only considers the thermal storage in a narrow application. Authors should enhance the applications aspects of solar-aided thermal storage of Renewable Energy 2022, 183, 406-422; Solar Energy Materials and Solar Cells 2022, , 111526; Solar Energy Materials and Solar Cells 2022, 236,111527; should also be commented. These applications using phase change materials are very useful for engineering applications such as the ones mentioned  in this paper”.

·   Also, the following papers are added according to the Second Previous Reviewer comment No. (1) as follows; “The rGO materials obtained from graphite have been reported in the past years. Moreover, the rGO/CuO composites are reported elsewhere.

   (See Rare Metals 40,1477-1493(2021), Rare Metals  

   40,3125-3134(2021), Rare Metals 41,911-920 (2022)).

   What is the advantage of material preparation or other  

    issue in study?. The novelty of this work should be

    highlighted in the Introduction part”.   

(1) “The synthesized reduced graphene oxide(rGO) is more fruitful in dyes depending on the electrostatic interaction between rGO and the dyes, [19–25].Chen et al. [2]used pi-ranha acid treatment at different time intervals with graphene oxide-silica particle nanocomposites.” It seems having nothing to do with the subject of the manuscript.

(2) “Zhao et al. [4] and Qian et al. [83] manufactured carbon electrode materials from agricultural and forestry biomass for super capacitor applications.” Such general statements should be avoided.

(2) These statements are avoided according to the Reviewer comment.

(3) Acronyms like ACS must be resolved in the text where they appear for the first time.

EXPERIMENTAL is not sufficiently described.

(3) The acronyms like ACS are resolved where they appear for the first time according to the Reviewer comment in GREEN color.

·   The EXPERIMENTAL is sufficiently according to the Reviewer comment in GREEN color.

(3.a) Synthesis of graphene oxide nano-particles – was it based on a procedure described in the literature?

تخليق جسيمات نانوية من أكسيد الجرافين - هل استند إلى إجراء موصوف في المؤلفات؟

(3.a) Synthesis of graphene oxide nano-particles  based on a procedure based  on the previous Researchers as described in the following literatures;

[1] Kotsyubynsky; V.O., Boychuk; V.M., Budzulyak; I.M., Rachiy; B.I., Zapukhlyak; R.I., Hodlevska; M.A., Kachmar; A.I., Bilogubka; O.R., and Malakhov; A.A., “Structural Properties of Graphene Oxide Materials Synthesized Accordingly to Hummers, Tour and Modified Methods: XRD and Raman Study”, PHYSICS AND CHEMISTRY OF SOLID STATE, V. 22, No. 1,  pp. 31-38, 2021.

[2] Naeem; H., Ajmal; M., Khatoon; F.,Siddiq; M.,and  Khan; G.S., “Synthesis of graphene oxide–metal nanoparticle nanocomposites for catalytic reduction of nitrocompounds in aqueous medium”,  JOURNAL OF TAIBAH UNIVERSITY FOR SCIENCE,  VOL. 15, NO. 1, pp. 493–506, 2021.

https://doi.org/10.1080/16583655.2021.1991736

[3] Gupta; D.K., Rajaura; R.S., and Sharma; K., “Synthesis and Characterization of Graphene Oxide Nanoparticles and their Antibacterial Activity”, Suresh Gyan Vihar University International Journal of Environment, Science and TechnologyVolume 1, Issue 1, 2015, pp.16-24, 2015.

ISSN:2394-9570.

[4] Kashinath; L., Kumar; R.S.,Hayakawa; Y.,  and G. Ravi; G., “Synthesis & Structural Study on Graphene Nano Particles”, International Journal of Science and Engineering Applications, 8, pp. 1-6, 2013. Special Issue NCRTAM ISSN-2319-7560 (Online), www.ijsea.com 8, DOI: 10.7753/IJSEANCRTAM.1003.

(3.b) Grass extract – how do authors know what the extract contain? No analysis was done.

(3.b)The grass extract contents and analysis are added according to the Reviewer comment under Sub. Title, “3.1. GC-MS Analysis and chemical composition of grass plant wastes”.

(3.c) No information of the rGO treatments at 20^oC, 300^oC, 350^oC, 400^oC, 450^oC and 500^oC that are discussed further.

(4) I suggest major revision aimed at Introduction and Experimental parts as well as language revision.

(f) All the summary repeated points at the Introduction and Experimental part are reviewed and corrected according to the Reviewer comments in GREEN color according to the Reviewer comment.

Reviewer No. (1)

English language and style

(x) Moderate English changes required

a. Does the introduction provide sufficient background and include all relevant references?

Must be improved.

b. Are all the cited references relevant to the research?

Can be improved.

c. Is the research design appropriate?

Can be improved.

d. Are the methods adequately described?

YES.

e. Are the results clearly presented?

YES.

f. Are the conclusions supported by the results?

YES.

·   The English language changes are shown in RED.

·   a. The introduction improved to provide sufficient background and 17 References are added, the changes are written in RED.

·   b. The References are improved to be relevant to the research, the changes are written in RED.

·   c. The research design be appropriate, the changes are written in RED.

·   d. Thanks to the Reviewer comment.

·   e. Thanks to the Reviewer comment.

·    

·   f. The conclusions supported by the results improved, the changes are written in RED.

Comments and Suggestions for Authors

1. Abstract: A brief introduction to the research background should be mentioned. The detailed descriptions on knowledge gap should also be shown here. Only the core results should be mentioned. Besides, authors should add more quantitative results to introduction to highlight the contribution. There should not be many abbreviations in abstract.

1. (a) A brief introduction to the research background be mentioned in the abstract according to the Reviewer comment in RED Color.

 (b) Detailed descriptions on knowledge gap be shown in the abstract according to the Reviewer comment in RED Color.

(c) The core results be mentioned shown in the abstract according to the Reviewer comment in RED Color.

(d) More quantitative results to introduction to highlight the contribution in the abstract according to the Reviewer comment in RED Color.

(e) Some abbreviations are omitted in the abstract according to the Reviewer comment in RED Color.

2. There are many typos for scientific writing. A native speaker should be referred to for language polishing. A good English writing should be provided for this paper.

2. The scientific writing typos are corrected, the language is polished and a good English writing is provided according to the Reviewer comment in RED Color.

3. The introduction part is not well written. The current study only considers the thermal storage in a narrow application. Authors should enhance the applications aspects of solar-aided thermal storage of Renewable Energy 2022, 183, 406-422; Solar Energy Materials and Solar Cells 2022, , 111526; Solar Energy Materials and Solar Cells 2022, 236,111527; should also be commented. These applications using phase change materials are very useful for engineering applications such as the ones mentioned  in this paper.

3. The introduction part enhances the application aspects of solar-aided thermal storage of the following References;

·   [10] Guo; J., Liu; Z., Yang; B., Yang; X., and Yan; J., “Melting assessment on the angled fin design for a novel latent heat thermal energy storage tube”, solar-aided thermal storage of Renewable Energy, 183, pp. 406-422, 2022.

·   [11] Guo; J. Wang; X., Yang; B., Yang; X. and Li; M.J., “Thermal assessment on solid-liquid energy storage tube packed with non-uniform angled fins”, Solar Energy Materials and Solar Cells, 111526, 2022.

·   [12] Yang; X.,   Wang; X.,   ZLiu; Z.,     Luo; X., and Yan^; J., “Effect of fin number on the melting phase change in a horizontal finned shell-and-tube thermal energy storage unit”, Solar Energy Materials and Solar Cells, 236 , 111527, 2022.

·   These References using phase change materials that are very useful for engineering applications in our paper.

4. What are the design criteria for the TES materials? How to define the size of the materials? The important info is missing.

4. The materials used are designed as followed;

a. To synthesis of graphene oxide; we used;

·  3 g of graphite powder; 69 mL of H₂SO₄ ((H₂SO₄; 99%), 1.8 g NaNO₃, and 9 g KMnO₄.

·  The resulting suspension volume mixture with 420 mL with double-distilled water and 9 mL of H₂O₂ (H₂O₂; 30%) until the suspension color turned from brown to bright yellow.

b. To Synthesis of CuO Nanoparticles

·   Grass plant wastes extracted, and stirred mechanically with 5000 rpm/min for 45 min .

·   The dried powder dispersed into 20 ml distilled water, boiled at 100^oC.

·   The filtered extract used as reducing agent and added drop by drop to copper sulphate  hexahydrate (5 grams) until the solution pH value adjusted to 8, according to [95].

·   The  mixture dissolved in 100 mL of the distilled water, sonicated for 40 min at room temperature.

·   Next, the mixture was heated up to 100 °C for 1 h and finally, the deposited  dark brown nanoparticles centrifuged (4000 rpm, 15 min), washed with the distilled water of  20 mL three times, and washed with 20 mL ethanol three times.

·    Finally the  obtained CuO nanoparticles dried in oven for 6hours at 60 °C in according to [61].

c. To synthesis of rGO-CuO Nanoparticles

·   To obtain rGO/CuO, a 2 mL GO solution at a concentration of 5 mg mL^-1  dropwised  and mixed with 300 mg CuO. The nanocomposite of GO/CuO was annealed at 400 ^oC for 4 h to reduce the GO into rGO and to get rGO/CuO composite.

d. rGO/CuO specimens

Four different rGO molarity concentrations of ; 0.125 M, 0.250 M, 0.500 M and 1.0 M dispersed separately in 5 mL of methanol, added to the 8 pH solution, continuously stirred for 2 hrs, washed with ethanol and water to remove the impurities and produced four precipitates.

5. What is the potential engineering application for the energy storage material in the current study?

5. The potential engineering application for the energy storage material in the current study is related to;

·  The future demands for off-grid power, high-performance electrochemical energy storage that based on earth-abundant materials is essential.

·  Supercapacitors are attractive in this sense due to their sustainable carbon-based architecture, rapid charging/discharging, and long cycle-life in comparison to battery chemistries.

·  So, carbon electrode materials from agricultural plant wastes have drawn great research attention for supercapacitor applications based on their lower cost, renewable nature, intrinsic porous structures, widespread availability, and environmental friendliness.

·  The high-performance supercapacitor devices made up with CuO as  positive electrode and rGO as negative electrode materials synthesized in a lower cost, simple and ecofriendly way are in utmost demand and the ultimate goal for widespread commercialization.

·  In our work, rGO-CuO composite active electrode material is achieved as green synthesis materials which not only performs as a very good supercapacitor but also demonstrates extremely well as a coin cell, and dye-sensitised solar Cells devices, that ready to use.

6. Why is a narrow temperature range from 0-30 degree considered in this study? If temperature increases, how is the energy storage material acting?

6. It is known according to; Bruno; and Shangc [55],  Diab [56] and Barnes and Levine [57] that; “ in the case of thermal characteristics of capacitors: The properties of this type of capacitor change with the change in temperature. It was found that the capacitance increases with the increase in temperature, while the resistance ESR decreases significantly with the increase in temperature. At lower temperatures, the ESR rises dramatically as a result of condensation of the electrolyte.”

Therefore, low temperatures used to identify the maximum decrease in the energy yield and determine the efficiency in this case.

References

[55] Bruno; G. and Shangc; J.L., “Current status of hybrid, battery and fuel cell electric vehicles: from electrochemistry to market prospects”, Journal of power sources, 84, 2011.

[56] Diab; Y., “Using energy storage systems for  improving therenewable energies performance”, First conf. Franco-Syrian on the Renewable Energies, Damascus, Syria, 2010.

[57] Barnes; F.S. and Levine; J.G. (eds.) , “ Large energy storage systems hand book”, CRC Press, 2011.

7. If the mass fraction of CuO increases a lot, what will be the energy storage performance?

7. According to;

·   Purushothaman et al. [78], “Cupric oxide (CuO) is a well-known metal oxide due to its special features such as non-toxicity, abundance, low cost and ease of fabrication in the form of nano dimensions, which have led to its use in Li-ion batteries and supercapacitor electrodes. However, its low electrical conductivity and destruction of the structure during ion intercalation/deintercalation have hampered the electrochemical performance of CuO”,  and “Graphene possessed  ultra-high specific surface area, high mechanical strength and elevated conductivity have led to its application in bio- and chemical sensors, field-effect transistors,16 energy storage devices, and bio medicine, …. etc”.

·  Keihan et al. [61] used a composite in a ratio of 2:1:1 of rGO, CuO, and PpPD, respectively. it is observed that the specific capacitance is remarkably increased to 512.12 F/g (at 1 A/g) on applying the rGO/CuO/PpPD-coated electrode with cyclic stability improved to 10 000 cycles.

·  Senthilkumar et al [63] showed that CuO electrode has higher energy and power density of 29.4 Wh/kg and 12.7 W/kg respectively, at 1.96 Ag-1 in an asymmetrical device, while Lu et al. [64] found that Electrodes using REGO (etched rGO) demonstrated a maximum energy density of 47 W h kg^_1,  while simultaneously displaying a high power density of up to 100 kW kg^-1 with considerable energy density.

·  So, “hybrid rGO/CuO nanocomposite exhibits a high specific capacitance of 326 F g^-1 at a current density of 0.5 A g^-1. It shows a high energy density of 65.7 W h kg-1 at a power density of 302 W kg^_1.Further, this material does not exhibit any measureable degradation in electrochemical performance, even after 1500 cycles. Symmetric hybrid capacitors exhibit a specific capacitance of 97 F g^-1 at 0.2 A g^-1 with a power density of 72 W kg^-1. These superior electrochemical features demonstrate that the CuO/RGO hybrid nanocomposite is a promising material for next-generation supercapacitor systems.

·   From all the previous work, we can say that increases the  mass fraction of rGO is better than increasing the mass fraction of CuO for increasing the energy storage performance

8. Marks should be added to the figures of SEM to show the difference.

8. The Marks be added to the figures of SEM according to the Reviewer comment.

9. Conclusions should be rewritten to highlight the core results in a list no more than 4 points.

9. The conclusions are rewritten to highlight the core results in a list no more than 4 points according to the Reviewer comment.

Reviewer No. (2)

English language and style

(x) English language and style are fine/minor spell check required.

a. Does the introduction provide sufficient background and include all relevant references?

Must be improved

b. Are all the cited references relevant to the research?

YES.

c. Is the research design appropriate?

X Can be improved.

d. Are the methods adequately described?

YES.

e. Are the results clearly presented?

YES.

f. Are the conclusions supported by the results?

YES.

·   The English language and style are extensively edited, the changes are shown in RED.

·   a. The introduction improved to provide sufficient background and 17 References are added, the changes are written in RED.

·  b. Thanks to the Reviewer comment.

·   c. The research design is improved according to the Reviewer comment in RED color.

·  d. Thanks to the Reviewer comment.

·  e. Thanks to the Reviewer comment.

·  f. Thanks to the Reviewer comment.

Comments and Suggestions for Authors

1. The rGO materials obtained from graphite have been reported in the past years. Moreover, the rGO/CuO composites are reported elsewhere.

(See Rare Metals 40,1477-1493(2021), Rare Metals 40,3125-3134(2021), Rare Metals 41,911-920 (2022)). What is the advantage of material preparation or other issue in study?

The novelty of this work should be highlighted in the Introduction part.

1. 1.The manuscript is rewritten and the data improved according to Reviewer (2) comment with the following references;.

·   Reference [77] Li; Y., Lu; Y.L., Wu; K.D., Zhang; D.Z., Debliquy; M., and Zhang; C., “Microwave-assisted hydrothermal synthesis of copper oxide-based gas-sensitive nanostructures”, Rare Met., 40 (6), pp. 1477–1493, 2021. https://doi.org/10.1007/s12598-020-01557-4

·   Reference [53] Chen; F., Feng; H.F., Luo; W., Wang; P., Yu; H.G., and Fan; J.J., “Simultaneous realization of direct photo-deposition and high H2-production activity of amorphous cobalt sulfide nanodot-modified rGO/TiO2 photocatalyst”, Rare Metals 2021, 40 (11) , pp. 3125-3134, 2021.  https://doi.org/10.1007/s12598-021-01755-8

·  Reference [54] Deng; B.L., Guo; L.P., Lu; Y., Rong; H.B., and Cheng; D.C., “Sulfur–nitrogen co-doped graphene supported cobalt–nickel sulfide rGO@SN-CoNi2S4 as highly efficient bifunctional catalysts for hydrogen/oxygen evolution reactions”, Rare Met., 41(3), pp. 911–920, 2022. https://doi.org/10.1007/s12598-021-01828-8

·  The novelty of this work be highlighted in the Introduction part as given in Research (1) comment.

2. The effect of grass plant wastes in the preparation of rGO/CuO composites should be explained in more details

2. The added papers with Numbers [15-17] explained the effect of green plants (like grass wastes) in the preparation of rGO and CuO (rGO/CuO composites).

·   New section  “2.3. Synthesis of CuO Nanoparticles” illstrate the effect of grass plant wastes in detail.

3. The scale bar in Figure 6, 7, and 8 should be repainted in order to be more distinct.

3. The scale bar in Figures 6, 7, and 8 repainted according to the Reviewer comment.

4. Some grammar errors and typos should be checked. Suggesting further polish the manuscript English.

4. The grammar errors and typos be checked and further polish of the English manuscript is corrected according to the Reviewer comment in RED color.

5. There is a blank between data and unit during the manuscript, which should be revised them.

5. The a blank between data and unit during the manuscript,  be revised according to the Reviewer comment.

Reviewer No. (3)

English language and style

(x) Extensive editing of English language and style required

a. Does the introduction provide sufficient background and include all relevant references?

Can be improved.

b. Are all the cited references relevant to the research?

X Must be improved.

c. Is the research design appropriate?

Must be improved.

d. Are the methods adequately described?

Must be improved.

e. Are the results clearly presented?

Must be improved.

f. Are the conclusions supported by the results?

Must be improved.

·   The English language and style are extensively edited, the changes are shown in RED.

·   a. The introduction improved to provide sufficient background with 17 References added, and the changes are written in RED.

·   b. The References are improved to be relevant to the research, the changes are written in RED.

·   c. The research design be appropriate, and the changes are written in RED.

·   d. The methods improved to be adequately described, the changes are written in RED.

·   e. The results are clearly improved, and the changes are written in RED.

·   f. The conclusions supported by the results improved, the changes are written in RED.

Comments and Suggestions for Authors

(a) Authors used a wrong method (crystallinity index, page 3, paragraph 4) to characterize rGO. The cited references are all cellulose related and apparently cellulose is different from rGO. rGO displayed quite broad peaks at XRD, not suitable to detect the crystallinity of rGO. Raman is the most important characterization to identify the quality of the rGO.

·        [92] Ju; X., Bowden; M., Brown; E.E., and Zhang; X., “An improved X-ray diffraction method for cellulose crystallinity measurement”, Carbohydr. Polym., 123, pp. 476–481, 2015.

             https://doi.org/10.1016/j.carbpol.2014.12.071.

·        [93] Agarwal; U.P., Ralph; S.A., Reiner; R.S., and Baez; C., “Probing crystallinity of never-dried wood cellulose with Raman spectrosco-py”, Cellulose, pp.1-20, 2015.    https://doi.org/10.1007/s10570- 015-0788-7.

·        [94] Segal, L.; Creely, J.J.; Martin, A.E., Jr.; Conrad, C.M., “An empirical method for estimating the degree of crystallinity of native cellulose using the x-ray diffractometer”, Text. Res. J., 29, pp. 786–794, 1959. https://doi.org/10.1177/004051755902901003.

But the following references used the crystallinity index method to characterize rGO, CuO and rGO/CuO;

·        [101]Kumari, V.; Kaushal, S.; Singh, P.P., “Green synthesis of a CuO/rGO nanocomposite using a terminalia arjuna bark extract and its catalytic activity for the purification of water”, Mater. Adv., 3, pp. 2170–2184, 2022.

 https://doi.org/10.1039/d1ma00993a.

·        [102] Li, D.; Liang, Z.; Zhang, W.; Dai, S.; Zhang, C., “Preparation and photocatalytic performance of TiO2-RGO-CuO/Fe2O3 ternary composite photocatalyst by solvothermal method”, Mater. Res. Express, 8, 015025, pp. 1-12, 2021. https://doi.org/10.1088/2053-1591/abdc3b.

·        [103] Gijare; M., Chaudhari; S., Ekar; S. and Anil Garje; A., “A facile synthesis of GO/CuO-blended nanofiber sensor electrode for efficient en-zyme-free amperometric determination of glucose”, Journal of Analytical Science and Technology,12:40, pp. 1-10, 2021.

·        [96] Pisarkiewicz; T, Maziarz; W., Małolepszy; A., Stobi’nski; L., Micho’n; D., and Rydosz; A., “Multilayer Structure of Reduced Graphene Oxide and Copper Oxide as a Gas Sensor”, Coatings, 10, 1015, pp. 1-13, 2020.

·        [104] Xu, X.; Shen, J.; Qin, J.; Duan, H.; He, G.; and Chen, H., “Cytotoxicity of Bacteriostatic Reduced Graphene Oxide-Based Copper Oxide Nanocomposites. JOM 2018, 71, 294–301. https://doi.org/10.1007/s11837-018-3197-1.

(b) Based on above, the Table 1, Figure 1, and Figure 2 are meaningless.

(b) Based on the up to date references numbers; [96 and 101-104] that explained in detail to Reviewer (2) comment No. (b), So, Table 1, Figure 1, and Figure 2 give a meaning of the effect of test temperature and periods on the crystallinity index of rGO, CuO and 1.0M rGO/CuO.

(c) The description of experiments are not clear. Page 4, section 2.3, 'Fresh grass plant extracted and used as a reducing agent', but there are no any description of how to treat/extract these grass and the main ingredient of extracted solution and other properties like pH, etc. Next sentence, 'copper sulphate dissolved in DI water', has no any info about the weight of CuSO4and volume of DI water, or in other words, the concentration of the solution. Therefore, these experiments are impossible to repeat.

(c) The description of experiments is corrected according to the Reviewer comment.

·     The description of how to treat/extract these grass and the main ingredient of extracted solution and other properties like pH, etc. are added under the title; “2.3. Synthesis of CuO Nanoparticles” of the revised article.

·     The information of the copper sulphate weight is given in section; “2.3. Synthesis of CuO Nanoparticles” .

·      The properties like pH are given in section; “2.3. Synthesis of CuO Nanoparticles” and section; “2.4. Synthesis of rGO-CuO Nanoparticles”.

·     The treat/extract of these grass weight is given in section “2.3. Synthesis of CuO Nanoparticles” .

·     The volume of DI water is given in section; “2.2. Synthesis of graphene oxide nano-particles” and  section “2.3. Synthesis of CuO Nanoparticles”.

·   The concentration of the solution is given in section “2.4. Synthesis of rGO-CuO Nanoparticles”.

(d) The interpreting SEM is totally wrong. Page 7, section 3.5, second sentence 'The dark are as related to graphite while the white areas related to O' is totally wrong. SEM image is to detect morphology not elements. The dark or white areas are related to conductivity difference or height difference (roughness). Nothing to do with elements.

(d) The following references and their figures used SEM image to detect elements on the morphology;

Sandhiran; N., Ganapathy; S., Manoharan; Y., Ganguly; D., Kumar; M., Ramanujam; K., and Balachandran; S., “CuO–NiO binary transition metal oxide nanoparticle anchored on rGO nanosheets as high-performance electrocatalyst for the oxygen reduction reaction”, Environmental Research

Volume 211, 112992, August 2022.

Gupta; M., Hawari; H.F., Kumar; P., and  Burhanudin; Z.A., “Copper Oxide/ Functionalized Graphene Hybrid Nanostructures for Room Temperature Gas Sensing Applications” Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 20 January 2022. © 2022 by the author(s). Distributed under a Creative Commons CC BY license.

·  Shashikumara; J.K.; Kalaburgi; B.,   Swamy; B.E.K., 

 Nagabhushana; H.,   Sharma; S.C. &   P. Lalitha; P., “Effect of RGO-Y₂O₃ and RGO-Y₂O₃:Cr³⁺ nanocomposite sensor for dopamine Effect of RGO-Y₂O₃ and RGO-Y₂O₃:Cr³⁺ nanocomposite sensor for dopamine”, Scientific Reports volume 11, Article number: 9372, 2021.

doi:10.20944/preprints202201.0300.v1

·   So, The interpreting SEM is not totally wrong in the case of relating the dark are to graphite and the white areas related to O.

(e) Fig. 7 are SEM images of CuO, but there is no any description of the preparation of CuO. These SEM images are strange. Room temperature, spherical, fine; but 300C, 500C becomes long rods. If annealing spherical CuO at 300C, the expected result is bigger particles or little irregular because of the agglomeration. It is hard to explain, unless other treatment, like hydrothermal, was involved.

5. The description of CuO  is given in section 2.3 as previously explained.

·   According to reference [102]; at room temperature, the morphology of Cu  and O are fine, round shaped,  uniform , dense, very smooth and their aggregates are almost spherical. They also showed tiny  nanoparticles tightly stuck together.

·  According to references [121-123]; with temperature increment (Fig. 7.b)  Cu (in dark) particles agglomerated, well-dispersed with regularly spherical shapes which means that                  temperature has significant effect on its structure morphology in agreement with Anwar et al. [121]     While O nanoparticles (in white) has a fibrous structure , with a mixture  of rods and needles like rod coupled with random orientation like sheaf feather mixture with  non-agglomerated morphologies in agreement with [122-123] .

·  According to reference [120]; at 500^oC ( Fig. 7.c), SEM micrograph  indicates well-dispersed and regularly spherical shapes of highly crystalline Cu nanoparticles. The  O nanoparticles showed an increment needle expanded shaped volumes due to temperature  increment in agreement.

·  The following figure of Ref. [121] illustratedthat at 500 C taking a needle shape (O) with Cu. In agreement of our work taking into consideration the magnification of the device.

·  So, SEM images explained CuO at room temperature,  300^oC, 500^oC is not wrong according to the  references.

·  Also; Ref. [121] and the following figure illustrated the effect of temperature on CuO

 [121]Anwar; H.,Naqvi; S.M.B., Abbas; B., M. Shahid; M., M. Iqbal; M, Shaharyar; M., Islam; A., F. Batool; F., M. Khalid; M., and A. Jamil; A., “in-vestigation of the effect of annealing temperature on structural, optical and antibacterial properties of copper oxide nanoparticles pre-pared by facile co-precipitation route”, Journal of Optoelectronic and Biomedical Materials, Vol. 12, No. 2, pp. 43 – 50, 2020.

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(f) EDS shows Cu peak but with less detectable carbon. so it is still a problem that the composition or the ratio between CuO/rGO.

(f) the EDS results are in a good agreement with the XRD analysis results where CuO/rGO has diffraction peaks closely aligned with the monoclinic phase of CuO corresponding to the planes (110), (111), (111), (202), (020), (202), and (311) (JCPDS 48-1548) and Sagadevan et al. [109] found that rGO/CuO peaks were consistent to the CuO peaks which illustrated the disappearance of carbon peaks in agreement with Refs.[107 and 110].

·  So, Cu peak appeared with less detectable carbon in the EDS which is in good agreement with XRD analysis.

·  The composion and the ratio between rGO/CuO explained in detail in section; “2.4. Synthesis of rGO-CuO Nanoparticles”.

(f) In summary, the authors claimed the preparation of rGO/CuO, unfortunately, (1) the preparation was not clear; (2) composition was not clear; (3) crucial characterisations like Raman was not done; (4) data interpretation was wrong including XRD and SEM; and (5) the performance of such prepared materials in supercapacitor (incentive of the study as mentioned in the introduction) is not clear. So this article is not good enough for the journal.

(f) All the summary repeated points are corrected according to the Reviewer comments in RED color at the Final Revised crystals 1860788.