Carbon Quantum Dot-Titanium Doped Strontium Ferrite Nanocomposite: Visible Light Active Photocatalyst to Degrade Nitroaromatics
Zhanhui Zhang
Round 1
Reviewer 1 Report
The authors have designed a Carbon quantum dots-titanium doped strontium ferrite nano-catalyst. The catalyst has been characterized by XRD, EDX, TEM, SEM, XPS, BET, VSM and IR analysis techniques. The activity of the catalyst was tested for degrade nitroaromatics. The interesting results would be useful to most of the readers of this journal. It probably merits publication in this journal. Other comments shown as follows are raised for further improving.
1) This work reports the application of ferrites and carbon dots. Related works should be mentioned, such as a) 10.1002/chem.202005138; b) 10.1016/j.cclet.2022.01.050; c) 10.1016/j.cclet.2021.03.026.
2) Suggest a mechanism for degradation with shematic.
3) All references should be checked again (author names, style, journal name, uppercase and lowercase, etc) again since I found some mistakes after a short, such as 1, 3, 3, 4, 7, 16, 23, 28 and 29.
Author Response
Comment: The authors have designed a Carbon quantum dots-titanium doped strontium ferrite nano-catalyst. The catalyst has been characterized by XRD, EDX, TEM, SEM, XPS, BET, VSM and IR analysis techniques. The activity of the catalyst was tested for degrade nitroaromatics. The interesting results would be useful to most of the readers of this journal. It probably merits publication in this journal. Other comments shown as follows are raised for further improving.
Reply: Thanks for the positive feedback.
Comment: This work reports the application of ferrites and carbon dots. Related works should be mentioned, such as a) 10.1002/chem.202005138; b) 10.1016/j.cclet.2022.01.050; c) 10.1016/j.cclet.2021.03.026.
Reply: Thanks for the suggestion. The suggested references have been cited in the revised manuscript, which are highlighted.
Comment: Suggest a mechanism for degradation with schematic.
Reply: Thanks for the suggestion. The plausible mechanism is suggested on the basis of quenching and gas chromatography-mass spectrometry. Photodegradation pathways of p-nitrophenol, pendimethalin and martius yellow have been presented as Scheme 1, 2 and 3. Schematic representation of Schottky heterojunction photocatalytic system between CQDs and Sr0.4Ti0.6Fe2O4.6 NPs has been added. Please see highlighted portion in section 2.3.2 and presented in Figure 7(e).
Comment: All references should be checked again (author names, style, journal name, uppercase and lowercase, etc) again since I found some mistakes after a short, such as 1, 3, 3, 4, 7, 16, 23, 28 and 29.
Reply: Thanks for the suggestion. All references have been re-checked and the corrections have been made as suggested.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this manuscript, Grewal and co-workers synthesized nanocomposites of carbon quantum dots (CQDs) with trimetallic strontium-titanium ferrite and investigated them in the photodegradation of three nitroaromatic model pollutants, namely p-nitrophenol, pendimethalin, and martius yellow. The authors found that the nanocomposite demonstrated the promising photocatalytic efficiency with 95.1, 97.5 and 92.0% for p-nitrophenol, pendimethalin, and martius yellow, respectively, under visible light irradiation. This reviewer supposes that it is an excellent study which could be published in Catalysts after minor revisions:
1. There are a few formatting and spelling mistakes.
2. The authors did not provide the adsorption capacity of nanocomposites towards model pollutants. It would be great to show the adsorption of organic compounds (quantitatively) since it is essential for photocatalysis.
3. The authors claim that a heterojunction is formed. It is necessary to indicate what type of heterojunction (type-I, II, III, Z-scheme, or S-scheme) is formed.
4. The authors should refer to more new literature and keep abreast of the latest research trends in the application of complex oxides in photocatalysis, e.g.: 10.1016/j.matlet.2022.133081; 10.1002/ente.202100302.
Author Response
Comment: In this manuscript, Grewal and co-workers synthesized nanocomposites of carbon quantum dots (CQDs) with trimetallic strontium-titanium ferrite and investigated them in the photodegradation of three nitroaromatic model pollutants, namely p-nitrophenol, pendimethalin, and martius yellow. The authors found that the nanocomposite demonstrated the promising photocatalytic efficiency with 95.1, 97.5 and 92.0% for p-nitrophenol, pendimethalin, and martius yellow, respectively, under visible light irradiation. This reviewer supposes that it is an excellent study which could be published in Catalysts after minor revisions:
Reply: Thanks for the positive outlook of the manuscript.
Comment: There are a few formatting and spelling mistakes.
Reply: Thanks for the suggestion. The suggested changes have been incorporated in the revised manuscript.
Comment: The authors did not provide the adsorption capacity of nanocomposites towards model pollutants. It would be great to show the adsorption of organic compounds (quantitatively) since it is essential for photocatalysis.
Reply: Thanks for the suggestion. The details of adsorption experiments have been given in section 3.3 and supplementary text S5. The quantitative evaluation of adsorption efficiencies has also been carried out and the discussion regarding the adsorption of organic compounds has been added and highlighted in supplementary text S5 and Fig. S3.
Comment: The authors claim that a heterojunction is formed. It is necessary to indicate what type of heterojunction (type-I, II, III, Z-scheme, or S-scheme) is formed.
Reply: Yes, the heterojunction is formed between CQDs and Sr0.4Ti0.6Fe2O4.6 NPs. It is a Schottky junction heterojunction system. The discussion indicating the type of heterojunction has been added and highlighted in section 2.3.2 in the revised manuscript.
Comment: The authors should refer to more new literature and keep abreast of the latest research trends in the application of complex oxides in photocatalysis, e.g.: 10.1016/j.matlet.2022.133081; 10.1002/ente.202100302.
Reply: Thanks for the suggestion. The suggested references have been cited in the revised manuscript and highlighted.
Author Response File: Author Response.pdf
