Wastewater Purification and All-Solid Z-Scheme Heterojunction ZnO-C/MnO2 Preparation: Properties and Mechanism
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Round 1
Reviewer 1 Report
The authors reported Z-scheme Heterojunction ZnO-C/MnO2 for degradation of tetracycline hydrochloride. However, some additional information and justification are required before it can be considered for publication.
1- English needs to be polished and grammar errors should be avoided.
2- The resolution of the axis label, axis numbers, and the letters inside the figures are blurred. I suggest inserting the figures with the original format instead of the picture format.
3- The authors did deconvolution of the O1s peaks. However, the "cumulative fit" peaks have not shown in the graphs. Please do deconvolution again.
4- The authors did explain parts of the photocurrent response and EIS analyses without any references to prove their claims.
5- The authors reported the work function values in Fig. 10a without clear evidence (UPS analysis). Please add the evidence of these values and correct the band alignment and charge carrier transfer mechanisms before and after heterojunction (Fig. 10 and Fig. 11).
6- Abstract and conclusion should be rewritten and show more clear results and novelty of this study.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this manuscript, ZnO-C/MnO2 ternary composites were prepared and investigated in the photocatalytic degradation of tetracycline hydrochloride (TC). The results are encouraging, but the paper could be published in Catalysts after the following revisions:
1. There are a few formatting and spelling mistakes.
2. The authors used a mercury lamp as light source. But the wavelength of light (λ > 420 nm or another) is not clear from the text of the manuscript.
3. It is necessary to indicate a crystallographic form of MnO2 which is formed during synthesis condition.
4. Figure 8 (a, c, d) shows the photocatalytic activity of materials during various reaction conditions. It can be seen that the main decrease in the TC concentration occurs in the first 30 min (indicated as 'dark reaction'). In the first 30 minutes, is it precisely the transformation of TC into products or its adsorption onto the surface of the composite?
a) If it is the transformation of TC during the first 30 min under dark conditions, what is the need for an additional light source?
b) If it is the adsorption, it is necessary to to explain the differences in adsorption under different conditions.
5. Can the authors study the main products formed during the decomposition of TC (e.g., using an HPLC technique)?
6. The authors should provide a table where the comparison of their results with other investigations will be presented.
7. The authors should refer to more new literature and keep abreast of the latest research trends associated with the use of MnO2 in photocatalysis, e.g.: 10.1016/j.solidstatesciences.2022.106997; 10.1007/s11356-019-07568-8.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have addressed all the comments I originally proposed. I would recommend the acceptance.
