Round 1

Reviewer 1 Report

Recommendation:

The authors present the photocatalytic degradation of Methylene Blue and Alizarin Red via doped NaTaO₃. The hydrothermal method was used to obtain and doped NaTaO₃ powder with metals: Fe, Ce, Ni, Mn and Bi. There are several points that need to be solved before I can recommend it for publication. Authors did a lot of characterization technics but the representation and analysis of the results need to be fulfilled and improved.

XRD analysis of catalysts

- How crystal parameters were calculated? Did the authors use Rietveld refinement or some other method?

- Row 96: „the intrinsic cell volume of NaTaO3 is 58.98 [A3],“ but in Table 1 is another value. What is correct?

- Row 97: „The cell volume decreases and the cell system becomes more stable.“ What authors mean by this statement?  Some references about that?  The decreasing volume cell from 58.85 to 58.83  can be in the error domain. What is the error?

XPS analysis of catalysis

- The authors did not show high-resolution spectra of every dopant that they claim was entering the lattice. What are the elements' oxidation states, and what are the atomic percentages of dopants? If Bi and Cs replace Na in NaTaO3, why are there no high-resolution Na spectra? The shift of Ta 4f is observed for Cs and Bi-dopant but for Fe, Ni and Mn is almost the same as pristine, so according to that it can not be said that it is a shift due to doping. What is an error of measurement?

- Rows 142-147: some references, better explanation of that statement. It can be concluded that all dopants increase oxygen vacancy only from the % of lattice oxygen. Some references? Which is the oxidation states of  Fe, Cs, Ni, Bi and how it changes the charge balance of the pristine sample. References for the statement that Mn indicates the presence of defects. Why the presence of Mn indicates defects but not other dopants, some references, or a correlation with other results?

SEM analysis

- Why there is mapping only for Cs dopant? What about others?

TEM analysis

- What is on figure 8g)? There is no dopant.

DRS analysis

- Why is in Figure 6 d) only VB for Ce, and what about other dopants?

Photocatalytic degradation

Figure 8 b) for Ce-NTO: authors claim that R2 is 0.9934 but there are only three points, three dots, what about the rest of the points, dots? Photocatalytic measurements were done with 7 measurements, seven concentrations of the solution at the time of reaction, so 7 points. Provide all 7 points for all samples and then see if is it really linear, maybe it is not a frist-order reaction.

 

Figure 8d for the green and blue lines shows a nonlinear relationship between time and ln(C/Co). It cannot be claimed that it follows the kinetic order as was written. This needs to be corrected. 

Author Response

Thanks to the editor for the opportunity to amend our manuscript. And we are truly grateful to your and other reviewers’ critical comments and thoughtful suggestions. Based on these comments and suggestions, we have made careful modifications on the original manuscript. All changes and additions in the manuscript text are marked with yellow highlight. These comments will be answered in turn.

 

Reviewers' comments:

Reviewer #1:

The authors present the photocatalytic degradation of Methylene Blue and Alizarin Red via doped NaTaO₃. The hydrothermal method was used to obtain and doped NaTaO₃ powder with metals: Fe, Ce, Ni, Mn and Bi. There are several points that need to be solved before I can recommend it for publication. Authors did a lot of characterization technics but the representation and analysis of the results need to be fulfilled and improved.

XRD analysis of catalysts

Question .1

- How crystal parameters were calculated? Did the authors use Rietveld refinement or some other method?

Response: Thank you for your questions. The crystal parameters of perovskite were calculated by using XRD parameters and Jade to analyze the cell parameters and cell volume of the catalyst. The rietveld refinement method was used.

Question .2

- Row 96: „the intrinsic cell volume of NaTaO₃ is 58.98 [A³],“ but in Table 1 is another value. What is correct?

Response: I'm very sorry for this error. We have checked the experimental data, the intrinsic cell volume of NaTaO₃ is 58.85 [A³].

Action Taken: The revised value was listed in line 96. The value of the cell volume for NaTaO₃ changed from 58.98 to 58.85

Question .3

- Row 97: „The cell volume decreases and the cell system becomes more stable.“ What authors mean by this statement?  Some references about that?  The decreasing volume cell from 58.85 to 58.83  can be in the error domain. What is the error?

Response: Thanks a lot for the questions. The decreasing of the cell volume means the shorter the bond length of the atoms. The shorter bond length leads to the stronger force between the atoms, so it is more stable. All the value of the volume cell was calculated by the software (Jade) automatically. We believe that all samples have the same systematic error.

XPS analysis of catalysis

Question .4

- The authors did not show high-resolution spectra of every dopant that they claim was entering the lattice. What are the elements' oxidation states, and what are the atomic percentages of dopants? If Bi and Cs replace Na in NaTaO₃, why are there no high-resolution Na spectra? The shift of Ta 4f is observed for Cs and Bi-dopant but for Fe, Ni and Mn is almost the same as pristine, so according to that it can not be said that it is a shift due to doping. What is an error of measurement?

Response: Thank you very much for your questions. The XPS spectra of O 1s, Fe 2p, Ce 3d, Ni 2p, Mn 2p and Bi 4f were added as Fig.S1 and Fig.S2 in the document of supporting Information. After XPS peak fitting, it can be found that Fe-doped NTO exists in the catalyst material in the form of Fe²⁺/Fe³⁺. Ce³⁺/Ce⁴⁺ exists in the Ce doped material. Ni exists in the catalyst material in the form of Ni²⁺/Ni³⁺. Mn doped NTO exists in the catalyst material in the form of Mn²⁺/Mn⁴⁺. For Bi-doped samlpe, Bi exists in the catalyst material with the form of Bi³⁺ and metallic Bi. The XPS quantitative results show that the atomic percentages for Bi is 2.96%, Ce is 2.74%, Fe is 3.85%, Ni is 3.67, Mn is 4.23% respectively. The low atomic percentages for Bi and Ce on the surface might indicate the different for the doped site in the structure. The XRD results (Fig.1(b)) show the obvious shift for all doped samples which implies the ions have been successfully doped into perovskite. Then, from IR result (Fig 2), the Ta-O-Ta absorption peaks are shifted to different degrees in the direction of high wave number, indicating that different metal doping will have a certain effect on the absorption peak position.  

Question .5

- Rows 142-147: some references, better explanation of that statement. It can be concluded that all dopants increase oxygen vacancy only from the % of lattice oxygen. Some references? Which is the oxidation states of Fe, Cs, Ni, Bi and how it changes the charge balance of the pristine sample. References for the statement that Mn indicates the presence of defects. Why the presence of Mn indicates defects but not other dopants, some references, or a correlation with other results?

Response: Thank you for your wise advice. The XPS spectra of O 1s, Fe 2p, Ce 3d, Ni 2p, Mn 2p and Bi 4f were added as Fig.S1 and Fig.S2 in the document of supporting Information. And the statement for this part was modified in the revised manuscript.

Action Taken:

1. The statement from line 142-147 was modified as follows:“Table 2 shows the percentage content of each oxygen species on the catalyst surface. The content of lattice oxygen increased for the doped sample except Mn-NTO, Ce doped sample increase most compared with NTO. Fe²⁺/Fe³⁺,Ce³⁺/Ce^4+, Ni²⁺/Ni³⁺ ,Mn²⁺/Mn⁴⁺ ,Bi³⁺ and metallic Bi were found in Fig.S2, which was consistent with the literature [27,28]. The lowest O^2- and highest O^-/O₂^- for Mn-NTO since the closest radius for Mn and Ta[28].
2. The References order was reassigned and new literatures [27][28] were added in the revised manuscript.

[27] C. L. Dong, H. Sun, Y Zhou, H. J. Zhan, G. Wang, W. Y. Liu, S. X. Bi, B. J. Ma, Transition metal (Ni, Cu, Ga, Fe) doped LaCoO₃ improve surface hydrogen activation to promote low-temperature CO₂ methanation, J. Environ. Chem. Eng. 2022, 10,107718.

[28] N.S. Al-Bassami, S.F. Mansour , E. Abdel-Fattah , M.A. Abdo,  Ce-Co-Mn-Zn ferrite nano catalyst: A synergetic effect of rare earth Ce³⁺ on enhanced optical properties and photocatalysis, Ceramics International, 2023,49, 20601-20612.

 

SEM analysis

Question .6

- Why there is mapping only for Ce dopant? What about others?

Response: Thank you for your questions. The mapping of the Ce doped sample was presented since this sample show the best degradation property. We only compared the undoped NTO sample and the Ce doped sample. There are many such practices in the literature(Chemical Engineering Journal 382 (2020) 123016).The other samples were not tested.

TEM analysis

Question .7

- What is on figure 5g)? There is no dopant.

Response: Thanks a lot for you question. The TEM figure 5(g) shows the Ni doped sample. According to the XPS result (Fig. S2), Ni exists in the catalyst material in the form of Ni²⁺/Ni³⁺. However, we did not found the lattice fringe of nickel oxide in the TEM image. This phenomenon appears in other literature as well（J Mater Sci: Mater Electron (2023) 34:1305）.

Question .8

- Why is in Figure 6 d) only VB for Ce, and what about other dopants?

Response: Thank you for your questions. The VB of Ce doped sample was presented since this sample show the best degradation property. Consider the issue of space, the VB of other catalysts will be presented in the support information as Fig. S3.

Figure S3. (a-f) VB XPS spectrum of the catalysts

 

Photocatalytic degradation

Question .9

Figure 8 b) for Ce-NTO: authors claim that R2 is 0.9934 but there are only three points, three dots, what about the rest of the points, dots? Photocatalytic measurements were done with 7 measurements, seven concentrations of the solution at the time of reaction, so 7 points. Provide all 7 points for all samples and then see if is it really linear, maybe it is not a frist-order reaction.

Response: We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. It belongs to the pseudo-first-order kinetic model ln(C /C₀)=kt which has been corrected in the paper.

Action Taken:

1. Line250-251: As shown in Figures 8b and d, the reaction between ln(C/C₀) and light time t conforms to quasi-first-order kinetics:ln(C/C₀) = kt （2-2）.

 

Question .10

Figure 8d for the green and blue lines shows a nonlinear relationship between time and ln(C/Co). It cannot be claimed that it follows the kinetic order as was written. This needs to be corrected.

Response: We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. It belongs to the pseudo-first-order kinetic model ln(C /C₀)=kt, there is no linear relationship between them which has been corrected in the paper.

Action taken: Amed " As shown in Figure.8 b and d, there is a good linear relationship between ln(C/C₀) and light time t, indicating that the photocatalytic degradation reactions of MB and ARS are in accordance with the pseudo first-orden kinetics: ln(C/C₀) = kt" to "As shown in Figures 8b and d, the reaction between ln(C/C₀) and light time t conforms to quasi-first-order kinetics :ln(C/C₀) = kt ",Page 9 , Line 249.

Author Response File: Author Response.docx

Reviewer 2 Report

The article is devoted to the study of the efficiency of photocatalytic oxidation of organic dyes by means of sodium tantalate doped with various metals. The article is of great practical and theoretical importance for the development of photocatalysts based on perovskite-type tantalum compounds. However, the article has a number of stylistic comments and some scientific data that are contradictory from the point of view of the reviewer. The article can be published after correcting the following comments:

 

1. Tidy up the numbering and formatting of formulas:

1.1. Line 207 and 249 - formulas are not numbered

1.2. The line 396 formula does not match the line 249 formula. Are these different formulas?

1.3. Why formulas are numbered (2-1, 2-2) ...line 390,396

 

2. Look carefully at the oxygen indices in the text of the article.

2.1. line 142. Index "2" for oxygen from below or above?

2.2. line 302 and figure 10c

 

3. Correct the use of abbreviations:

3.1. no decryption PL, TEMPO, DEMPO, EPR

3.2. on line 73 enter the abbreviations MB and ARS

3.3. What is the "S" in ARS for Alizarin red?

 

4. In the caption to figures 9 and 10, indicate which sample was studied and on which dye.

 

5. Where is figure 12? line 305

 

6. Why Photovoltaic characterization of catalysts when this subsection investigates photoluminescence?

 

7. On the basis of what do the authors suggest that cerium transforms from 3+ to 4+ during light irradiation in Figure 11?

 

8. For what reasons do all the studied samples lose photoactivity when approaching the concentration of alizarin red in 0.2 in Fig. 8c. However, the authors test the cyclic activity of the cerium sample precisely on alizarin red.

The degradation rate of the catalyst decreased after four consecutive cycles of  degrading ARS (Figure 9a), but still reached 78%. 

9. The authors claim:

As shown in Figure.8 b and d, there is a good linear relationship between ln(C/C 0 ) and

However, the points for the cerium and nickel samples have a non-linear dependence in Figure 8d

9.1. Why do the authors use experimental points up to 120 minutes in Figure 8d when the kinetics are shown up to 180 minutes in Figure 8c? Probably because when using points up to 180 minutes, the curve on the 8d graph will be completely non-linear?

9.2. Correct the text or justify the choice of the number of experimental points up to 120 minutes in Figure 8d.

 

10. Explain the contradiction:

It is known that the higher the intensity of photoluminescence, the higher the rate of recombination of electron-hole pairs and the worse photocatalysis.

It is known that the larger the band gap, the less visible light is absorbed by the photocatalyst for generating electron-hole pairs.

However:

- the authors in Figure 7 show the third highest photoluminescence intensity in the cerium composite

- Figure 6b shows the second largest zone width of 3.8 (for example, for thianium oxide it is 3.1-3.6)

- in Figure 8, ac show the best photoactivity of the cerium photocatalyst

- in the conclusions they write that the cerium catalyst has a weak recombination of electron holes

The presented results and their interpretation in terms of photoluminescence, catalytic activity, and absorption spectra mislead the reader about the reasons for the high activity of the cerium photocatalyst.

 

 

Minor editing of English language required

Author Response

Reviewer #2:

The article is devoted to the study of the efficiency of photocatalytic oxidation of organic dyes by means of sodium tantalate doped with various metals. The article is of great practical and theoretical importance for the development of photocatalysts based on perovskite-type tantalum compounds. However, the article has a number of stylistic comments and some scientific data that are contradictory from the point of view of the reviewer. The article can be published after correcting the following comments:

1. Tidy up the numbering and formatting of formulas:

1.1. Line 207 and 249 - formulas are not numbered

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors and made detailed corrections to similar issues in the manuscript.

Action taken

1. Page 7, Line 209, E_CB=E_VB-E_g （2-1）
2. Page 99, Line 250, ln(C/C₀) = kt （2-2）
3. Page 14, Line 391, (4-1)
4. Page 14, Line 397, (4-2)

 

1.2. The line 396 formula does not match the line 249 formula. Are these different formulas?

Response：We thank the reviewer’s comments. Our response to this question is as follows: In order to quantitatively compare the reaction kinetics of the photocatalytic degradation of the above samples, the pseudo-first-order kinetic model ln(C/C₀)=kt was used for linear fitting analysis. The formula is deformated during data processing :-ln(C /C₀)=kt.

1.3. Why formulas are numbered (2-1, 2-2) ...line 390,396

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors and made detailed corrections to similar issues in the manuscript.

Action taken

1. Page 14, Line 391, (4-1)
2. Page 14, Line 397, (4-2)
3. Look carefully at the oxygen indices in the text of the article.

2.1. line 142. Index "2" for oxygen from below or above?

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. It has been amended in line 140.

Action taken:.

Page 5, Line 140, ''lattice oxygen (O₂^-) '' should be replaced by ''lattice oxygen (O^2-)''

2.2. line 302 and figure 10c

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. It has been amended in line 304.

Action taken:

Page 12, Line 304, '' Figure 10. (a) Catalyst radical capture experiment; (b) DMPO - O₂^- ; (c) DMPO- ·OH ; (d) DMPO- h⁺'' should be replaced by '' Figure 10. (a) Catalyst radical capture experiment; (b) DMPO- h+; (c)DMPO - ·O2- ; (d) DMPO- ·OH''

3. Correct the use of abbreviations:

3.1. no decryption PL, TEMPO, DMPO, EPR

Response：Thanks a lot for your question. The full names of the PL, TEMPO, DMPO, EPR were added in the revised manuscript in the first appearance to make it clearer to the readers. PL: photoluminescence, DMPO: 5,5-Dimethyl-1-pyrrolidine N-oxide, TEMPO: 2,2,6,6-Tetramethylpiperidinooxy, EPR:Electron paramagnetic resonance.

Action Taken:

1. Line 220, change 2.1.7. Photoluminescence to “Photoluminescence (PL)”.
2. Line2995, DMPO: 5,5-Dimethyl-1-pyrrolidine N-oxide.
3. Line295, TEMPO: 2,2,6,6-Tetramethylpiperidinooxy.
4. Line302, EPR:Electron paramagnetic resonance.

 

3.2. on line 73 enter the abbreviations MB and ARS

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. It has been amended in line 73.

Action taken:

Page 2, Line 73, "methylene blue and alizarin red" should be replaced by "methylene blue (MB)and alizarin red S(ARS) "

3.3. What is the "S" in ARS for Alizarin red?

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. The correct spelling is alizarin red S(ARS).

4. In the caption to figures 9 and 10, indicate which sample was studied and on which dye.

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. This article has been modified, and the correct title is: "Figure 9. (a) Ce-NTO degradation of AR cycle experiment; (b) XRD comparison of catalyst Ce-NTO before and after use. "

5. Where is figure 12? line 305

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors.

Action taken

Page 12, Line 307, '' Figure 12'' replaced by '' Figure 11''.

6. Why Photovoltaic characterization of catalysts when this subsection investigates photoluminescence?

Response：Thank you very much for your question. The photoluminescence spectra refer to the use of light as an exciting means to excite electrons in the materials. The process of luminescence appears, which is a phenomenon that occurs with the addition of photogeneration in the process of remaining pairs coincidence. The photoluminescence spectra can reflect the recombination of electrons and holes in the excitation process. Moreover, the recombination of electrons and holes is a significant factor for the photocatalytic process.

 

7. On the basis of what do the authors suggest that cerium transforms from 3+ to 4+ during light irradiation in Figure 11?

Response：We would like to thank the reviewers for their valuable comments. Our response to this question is as follows: (1) Doped metal cerium is introduced in the form of nitric acid, and Ce exists in the form of Ce³⁺ in Ce(NO₃)₃•6H₂O；(2) After XPS peak fitting, it can be found that Ce in Ce doped NTO exists in the form of Ce³⁺/Ce⁴⁺ in the catalyst material (3) Metal Ce doped in the form of rod and particle agglomeration around the cubic structure. After local magnification, it was found that the lattice was interlaced, and Ce was agglomerated around the perovskite in the form of CeO₂ after measurement.

      

8. For what reasons do all the studied samples lose photoactivity when approaching the concentration of alizarin red in 0.2 in Fig. 8c. However, the authors test the cyclic activity of the cerium sample precisely on alizarin red.

The degradation rate of the catalyst decreased after four consecutive cycles of degrading ARS (Figure 9a), but still reached 78%

Response：We would like to thank the reviewers for their valuable comments. Fig. 8c shows the best degradation rate for Ce-NTO sample, the concentration of alizarin red decreased to 0.2 within 60 min, which means a 80% degradation rate. Commonly, catalyst surface active species are covered or exhausted will make it inactivation. This kind of inactivation is more likely occur for the catalyst with best performance. This is the reason for the stability test of Ce doped sample. (Catalysis Letters https://doi.org/10.1007/s10562-023-04297-z)

9. The authors claim:

As shown in Figure. 8b and d, there is a good linear relationship between ln(C/C 0 ) and

However, the points for the cerium and nickel samples have a non-linear dependence in Figure 8d

Response: We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. It belongs to the pseudo-first-order kinetic model ln(C /C₀)=kt, there is no linear relationship between them which has been corrected in the paper.

Action taken: Amed " As shown in Figure.8 b and d, there is a good linear relationship between ln(C/C₀) and light time t, indicating that the photocatalytic degradation reactions of MB and ARS are in accordance with the pseudo first-orden kinetics: ln(C/C₀) = kt" to "As shown in Figures 8b and d, the reaction between ln(C/C₀) and light time t conforms to quasi-first-order kinetics :ln(C/C₀) = kt ",Page 9 , Line 249.

 

9.1. Why do the authors use experimental points up to 120 minutes in Figure 8d when the kinetics are shown up to 180 minutes in Figure 8c? Probably because when using points up to 180 minutes, the curve on the 8d graph will be completely non-linear?

Response：We would like to thank the reviewers for their valuable comments. Our response to this question is as follows：(1) The experimental process accords with pseudo-first-order dynamics, but it is not linearly correlated;(2) Figure 8d shows the kinetic curve of photocatalytic degradation of alizarin red. The experimental process lasted for 180min, but the degradation tended to be stable in 120-180 min. Therefore, we believed that the pseudo-first-order kinetics was more consistent in the first 120min.

 9.2. Correct the text or justify the choice of the number of experimental points up to 120 minutes in Figure 8d. 

Response：Thanks a lot for your opinion. The experimental process lasted for 180min, but the degradation tended to be stable in 120-180 min. Therefore, we believed that the pseudo-first-order kinetics was more consistent in the first 120min.

Action taken: Amed " As shown in Figure.8 b and d, there is a good linear relationship between ln(C/C₀) and light time t, indicating that the photocatalytic degradation reactions of MB and ARS are in accordance with the pseudo first-orden kinetics: ln(C/C₀) = kt" to "As shown in Figures 8b and d, the reaction between ln(C/C₀) and light time t conforms to quasi-first-order kinetics :ln(C/C₀) = kt ",Page 9 , Line 249.

10. Explain the contradiction:

It is known that the higher the intensity of photoluminescence, the higher the rate of recombination of electron-hole pairs and the worse photocatalysis.

It is known that the larger the band gap, the less visible light is absorbed by the photocatalyst for generating electron-hole pairs.

However:

- the authors in Figure 7 show the third highest photoluminescence intensity in the cerium composite

- Figure 6b shows the second largest zone width of 3.8 (for example, for thianium oxide it is 3.1-3.6)

- in Figure 8, ac show the best photoactivity of the cerium photocatalyst

- in the conclusions they write that the cerium catalyst has a weak recombination of electron holes

The presented results and their interpretation in terms of photoluminescence, catalytic activity, and absorption spectra mislead the reader about the reasons for the high activity of the cerium photocatalyst.

Response：We would like to thank the reviewers for their valuable comments. Our response to this question is as follows: (1) The lower peak of photoluminescence means the lower electron-hole pair recombination rate and the stronger the photocatalytic performance. The photoluminescence strength of the Ce doped catalyst is significantly lower than that of the intrinsic NTO, indicating that the introduction of doping can inhibit the electron-hole pair recombination. (2) The narrow band gap is conducive to improving the light absorption capacity, but does not necessarily lead to the quality of photocatalytic activity. It tends to a certain limitation. (3) There are many factors affecting the photocatalytic performance, such as band gap, electron hole pair recombination rate, electron migration rate, interface condition, etc. The final photocatalytic activity may be the result of synergistic for different factors.

 

Author Response File: Author Response.docx

Reviewer 3 Report

This work presents the synthesis of metal-doped NaTaO3 materials, which present slight improvements in the photocatalytic activity compared to the unmodified NaTaO3 material. The characterization of the materials is good and well discussed. However, authors have problems discussing the photocatalytic performance of the materials in the degradation of dyes. Major revisions are necessary.

Line 85. It is possible that Bi appear in the XRD due to the reduction of Bi3+ in the calcination step as it is a readily reducible element at temperatures above 500 °C.

Please change the term “electron-hole complexation” by recombination.

In section 2.1.3. XPS signals are not diffraction peaks. Please correct this.

In Table 2. Change absorb by adsorbed.

Please explain what was the theoretical and actual loadings of doping elements in the NaTaO3 perovskite. EDS results can aid to obtain such information.

XPS can be a useful tool to demonstrate the occurrence of Ce and Mn oxides within the NaTaO3 lattice,

Figure 6b. Only the Fe- and Mn-doped materials were able to photoactivate under visible light irradiation. This must be stated in te manuscript.

Lines 206 to 211. Please improve the writing in this paragraph as it is somehow confusing.

In section 2.1.7. This is not a photovoltaic characterization of the materials, as it is an optical test measuring photoluminescence to determine the recombination rate of the charge carriers.

Please explain the meaning of ARS. It refers to alizarin red, but it must be clarified as it is not so obvious as occurs with MB.

It is strange that Ce-, Ni- and Bi-doped materials were photoactive under visible light irradiation considering their wide band gap. Please provide the emission spectrum of the lamp used in photocatalytic tests, as it maybe provides some UV light irradiation.

Line 246. It is “pseudo first-orden kinetics”. Please correct.

Lines 248 to 257. Please avoid repeating the information provided in Tables and Figures.

Lines 258 to 261. It is redundant. Please remove.

Line 268. It is not a real correlation. The wider band gap does not necessarily leads to a better or worse photocatalytic activity as this parameter only indicates whether or not the semiconductor is activated under visible light. The activity of the charge carriers presents a different behavior.

Please present evidence on the formation of •OH radicals, for instance the terephthalic acid test. It is strange that these radicals have no effect in the photocatalytic process, when when they are produced upon photoexcitation of the semiconductor.

Lines 310 to 312. There is a misunderstanding on the role of photo-holes in the photocatalytic performance. The results of the scavengers tests have shown that •OH radicals have litthe effect in the degradation of the dye while holes are more active. That does not mean that photo holes are relevant as they oxidize water and produce •OH radicals. Please correct this part.

Ce-doped NaTaO3 presents a band gap value of 3.80 eV. It is impossible that it photo-activate under visible light irradiation, and thus doping is not increasing its photocatalytic activity under visible light irradiation. It is most likely that oxygen vacancies do reduce the charge carrier recombination but it does not boost the activity under visible light irradiation, so materials are not able to use sunlight by this kind of doping. Please correct the discussion of this point in section 2.3.

Please re-write the Conclusions section as it only presents a summary of the results instead of the main conclusions drawn from the analysis of results.

English must be revised and improved as some parts are hard to follow. 

Author Response

Reviewer #3:

This work presents the synthesis of metal-doped NaTaO₃ materials, which present slight improvements in the photocatalytic activity compared to the unmodified NaTaO₃ material. The characterization of the materials is good and well discussed. However, authors have problems discussing the photocatalytic performance of the materials in the degradation of dyes. Major revisions are necessary.

 

Line 85. It is possible that Bi appear in the XRD due to the reduction of Bi³⁺ in the calcination step as it is a readily reducible element at temperatures above 500 °C.

Response：Thank you very much for your comments. As the reviewer mentioned, Bi can be found in both the results of XRD (Fig.1) and XPS (Fig. S2). The XPS spectra Fe 2p, Ce 3d, Ni 2p, Mn 2p and Bi 4f were added as Fig.S1 and Fig.S2 in the document of supporting Information. And the statement for this part was modified in the revised manuscript.

Action Taken:

1. The statement from line 142-147 was modified as follows:“Table 2 shows the percentage content of each oxygen species on the catalyst surface. The content of lattice oxygen increased for the doped sample except Mn-NTO, Ce doped sample increase most compared with NTO. Fe²⁺/Fe³⁺,Ce³⁺/Ce^4+, Ni²⁺/Ni³⁺ ,Mn²⁺/Mn⁴⁺ ,Bi³⁺ and metallic Bi were found in Fig.S2, which was consistent with the literature [27,28]. The lowest O^2- and highest O^-/O₂^- for Mn-NTO since the closest radius for Mn and Ta[28].
2. The References order was reassigned and new literatures [27][28] were added in the revised manuscript.

[27] C. L. Dong, H. Sun, Y Zhou, H. J. Zhan, G. Wang, W. Y. Liu, S. X. Bi, B. J. Ma, Transition metal (Ni, Cu, Ga, Fe) doped LaCoO₃ improve surface hydrogen activation to promote low-temperature CO₂ methanation, J. Environ. Chem. Eng. 2022, 10,107718.

[28] N.S. Al-Bassami, S.F. Mansour , E. Abdel-Fattah , M.A. Abdo,  Ce-Co-Mn-Zn ferrite nano catalyst: A synergetic effect of rare earth Ce³⁺ on enhanced optical properties and photocatalysis, Ceramics International, 2023,49, 20601-20612.

 

Please change the term “electron-hole complexation” by recombination.

In section 2.1.3. XPS signals are not diffraction peaks. Please correct this.

In Table 2. Change absorb by adsorbed.

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors and made detailed corrections to similar issues in the manuscript.

Action taken:

1. Page 3, Line 111, ''electron-hole complexation'' replaced by ''electron-hole recombination''
2. Page 8 , Line 221, ''electron-hole complexation'' replaced by ''electron-hole recombination''
3. Page 13 , Line 333, ''electron-hole complexation'' replaced by ''electron-hole recombination''
4. Page 14 , Line 372, ''electron-hole complexation'' replaced by ''electron-hole recombination''
5. Page 44, Line 125, ''the diffraction peaks are mainly concentrated in '' replaced by ''the peaks were mainly concentrated in''
6. Table 2. ''Absorb'' replaced by ''Adsorbed''

 

Please explain what was the theoretical and actual loadings of doping elements in the NaTaO₃ perovskite. EDS results can aid to obtain such information.

Response：Thanks a lot for the comments. The quantity of raw materials for the loadings are the sample for 0.1mol M(M=Fe、Ce、Ni、Mn、Bi). The XPS quantitative results show that the atomic percentages for Bi is 2.96%, Ce is 2.74%, Fe is 3.85%, Ni is 3.67, Mn is 4.23% on the surface of the samples, respectively.

 

XPS can be a useful tool to demonstrate the occurrence of Ce and Mn oxides within the NaTaO₃ lattice.

Response：Thank you for your guidance. The XPS spectra of O 1s, Fe 2p, Ce 3d, Ni 2p, Mn 2p and Bi 4f were added as Fig.S1 and Fig.S2 in the document of supporting Information. After XPS peak fitting, it can be found that Fe-doped NTO exists in the catalyst material in the form of Fe²⁺/Fe³⁺. Ce³⁺/Ce⁴⁺ exists in the Ce doped material. Ni exists in the catalyst material in the form of Ni²⁺/Ni³⁺. Mn doped NTO exists in the catalyst material in the form of Mn²⁺/Mn⁴⁺. For Bi-doped samlpe, Bi exists in the catalyst material with the form of Bi³⁺ and metallic Bi. The XPS quantitative results show that the atomic percentages for Bi is 2.96%, Ce is 2.74%, Fe is 3.85%, Ni is 3.67, Mn is 4.23% respectively.

Figure 6b. Only the Fe- and Mn-doped materials were able to photoactivate under visible light irradiation. This must be stated in the manuscript.

Response：We would like to thank the reviewers for their valuable comments. We benefited from careful review by reviewers who corrected the errors for us in a timely manner. We conducted a timely review of the manuscript and re-elaborated on the above issues.

Action taken: Add ''The absorption edges of the 5 groups of elements doped showed different degrees of redshift. The light response of Fe and Mn doped NaTaO₃ is expanded from the original pure ultraviolet light response to the visible light region. Lines 206 to 211. Please improve the writing in this paragraph as it is somehow confusing'' On Page 7, Lines 197 to 200.

 

In section 2.1.7. This is not a photovoltaic characterization of the materials, as it is an optical test measuring photoluminescence to determine the recombination rate of the charge carriers.

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors.

Action taken

Page 8, Line 216, ''Photovoltaic characterization of catalyst'' replaced by ''photoluminescence''

 

Please explain the meaning of ARS. It refers to alizarin red, but it must be clarified as it is not so obvious as occurs with MB.

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors. It should be alizarin red S.

Action Taken:

1.Line 74: alizarin red S(ARS)

It is strange that Ce-, Ni- and Bi-doped materials were photoactive under visible light irradiation considering their wide band gap. Please provide the emission spectrum of the lamp used in photocatalytic tests, as it maybe provides some UV light irradiation.

Response.: We would like to thank the reviewers for their valuable comments. We benefited from careful review by reviewers who corrected the errors for us in a timely manner. We have checked the manuscript in time, the experiment was completed by mercury lamp. The spectrum of the mercury lamp is concentrated in the UV-visible band of 250-600nm, and the wavelength of the stronger light source is 350-450 nm and 550-600 nm.

 

Line 246. It is “pseudo first-orden kinetics”. Please correct.

Response: We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors.

Action taken

Page 99, Line 248, '' first-order reaction kinetics '' replaced by '' pseudo first-orden kinetics ''

Lines 248 to 257. Please avoid repeating the information provided in Tables and Figures.Lines 258 to 261. It is redundant. Please remove.

Response: Thanks a lot for your comments. The repeating the information provided in Tables and Figures from line 248-257 was revised and the redundant statement from line 258 to 261 is removed.

The results show that the introduction of metal can effectively reduce the band gap value of NaTaO₃, and narrow band gap is beneficial to improve the light absorption capacity of the material. Among them, the optical response of Fe, Ce, Ni, Mn and Bi doped NaTaO₃ is broadened from the original NaTaO₃ pure ultraviolet light response to the visible light region.

Line 268. It is not a real correlation. The wider band gap does not necessarily leads to a better or worse photocatalytic activity as this parameter only indicates whether or not the semiconductor is activated under visible light. The activity of the charge carriers presents a different behavior.

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors.

Action taken：

1、Amend “the wider the band gap, the better the photocatalytic efficiency, but tended to a certain limit” to “the narrow band gap is conducive to improving the light absorption capacity, but does not necessarily lead to better or worse photocatalytic activity. It tends to a certain limit.” On Page 10, Line 270

Please present evidence on the formation of •OH radicals, for instance the terephthalic acid test. It is strange that these radicals have no effect in the photocatalytic process, when they are produced upon photoexcitation of the semiconductor.

Response：Thank you very much for you wise advises. The radical capture experiment can confirm the existence of •OH radicals (Fig 10 (a)). During the experiment, IPA concentration was not screened and was only added to the system according to the same concentration as other trapping agents, but the limit concentration of IPA was not reached, so the inhibition effect was not obvious in this experiment. The EPR results also show the signal of •OH radicals (Fig 10 (d)). However, after EDTA-2Na adding, the degradation process was significantly inhibited, and the degradation rate was greatly reduced, indicating that the holes played a major role in the degradation process.

Lines 310 to 312. There is a misunderstanding on the role of photo-holes in the photocatalytic performance. The results of the scavengers tests have shown that •OH radicals have little effect in the degradation of the dye while holes are more active. That does not mean that photo holes are relevant as they oxidize water and produce •OH radicals. Please correct this part.

Response：Thank you so much for your wise advice. The statements from line 310 to 312 were revised.

Action Taken:

From line 310: These produce more oxygen vacancies and reduce carrier recombination. Thus, as the composite is irradiated by visible light, the excited electrons jumped from O 1s to Ta5d orbital to from the žO₂^-. And the holes on valence band can form •OH with water molecules which adsorbed on the catalysts surface. Therefore, the holes play a crucial role in the photocatalytic process, which can decompose the dye into small molecules. The addition of metals effectively inhibits the photoelectron-hole recombination and improves the photocatalytic performance of the materials.

Ce-doped NaTaO₃ presents a band gap value of 3.80 eV. It is impossible that it photo-activate under visible light irradiation, and thus doping is not increasing its photocatalytic activity under visible light irradiation. It is most likely that oxygen vacancies do reduce the charge carrier recombination but it does not boost the activity under visible light irradiation, so materials are not able to use sunlight by this kind of doping. Please correct the discussion of this point in section 2.3.

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors.

Action taken：

1、Amend “These produce more oxygen vacancies, reduce the forbidden band width of the sample and increase the response range to visible light.” to “These produce more oxygen vacancies and reduce carrier recombination.” On Page 12, Line 309

2、Amend “The introduction of metals, however, effectively suppresses the photogenerated electron-hole recombination while reducing the band gap, exploiting the broad spectral region and ultimately realizing the full utilization of solar energy..” to “The addition of metals effectively inhibits the photoelectron-hole recombination and improves the photocatalytic performance of the materials” On Page 12, Line 314

 

Please re-write the Conclusions section as it only presents a summary of the results instead of the main conclusions drawn from the analysis of results.

English must be revised and improved as some parts are hard to follow. 

Response: We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors. We modified the conclusion section in the revised manuscript.

Action Taken:

1. The conclusion section was re-written as follows:“The series NaTaO₃ perovskite modified with five different metal elements were prepared with hydrothermal method and applied for photocatalytic degradation. The structural test results indicate Na⁺ was partially replaced by Bi and Ce in A-position of the perovskite. And Fe, Ni and Mn partially replace Ta⁵⁺ doped into the B-position of NaTaO₃. The metal doping forms an intermediate energy band, which reduces the band gap of NTO and decreases the photogenerated electron-hole recombination rate. The Ce-NTO sample showed the best photocatalytic degradation performance with narrower band gap, high migration rate of photogenerated carriers and weak recombination of photogenerated charges and holes. The holes play a crucial role in the photocatalytic process, which can decompose the dye into small molecules.”

Author Response File: Author Response.docx

Reviewer 4 Report

Manuscript number: Catalysts-2515001

Title: Visible light photocatalytic degradation performance of metal 2 (Fe, Ce, Ni, Mn, Bi)-doped sodium tantalite perovskite

In the manuscript, authors described the synthesis of NaTaO3 perovskite catalyst with good structural and catalytic properties by a simple hydrothermal reaction  method. The authors also introduced Bi, Ce, Mn, Ni and Fe into NaTaO3 perovskite structure in order to investigate the effects of the dopants on the structure and enhance the photocatalytic performances of the catalysts named as Bi-NTO, Ce-NTO, Mn-NTO, Ni-NTO and Fe-NTO respectively. The morphology and characterization of the catalysts were obtained and discussed well with XRD, FTIR, SEM, TEM, XPS, DRS and EPR. The visible light induced photocatalytic activities of catalysts were studied by the photocatalytic degradation of MB and ARS.

The following comments should be addressed in order to be evaluated for publication in Catalysts.

1.      There is no comparison for the photocatalytic performance of the catalysts with similar articles. Authors should give a comparison in a table in the discussion part to help readers to understand and compare the visible light induced photocatalytic activity of the prepared catalysts.

2.      The effect of catalyst amount on the dye degredation should be given according to the experiments. Also the effect of doping amount may be for Ce only should be given.

3.      The XPS core-level spectrum is only given for Ta4f. The other core-level spectra should be given and the deconvolutions and related discussions should be made. Also the percentages of all elements that is obtained by XPS should be given as a Table.

4.      The authors only gave the results of reusability experiments for Ce-NTO. It will be better to mention the reusability results of the other catalysts synthesized in the manuscript.

5.      Could the authors please explain how they controlled the temperature of the reaction medium in experimental part?

6.      The band gap values of NaTaO3 and Ce-NTO were calculated as different values from DRS and VB-XPS. Could you please explain why these two calculations gave different results?

7.      There are many grammatical and typing errors in the text and in the figure captions that need to be re-checked and corrected more carefully.

 

 

Comments for author File: Comments.pdf

Minor editing is required.

Author Response

Reviewer #4:

In the manuscript, authors described the synthesis of NaTaO3 perovskite catalyst with good structural and catalytic properties by a simple hydrothermal reaction  method. The authors also introduced Bi, Ce, Mn, Ni and Fe into NaTaO3 perovskite structure in order to investigate the effects of the dopants on the structure and enhance the photocatalytic performances of the catalysts named as Bi-NTO, Ce-NTO, Mn-NTO, Ni-NTO and Fe-NTO respectively. The morphology and characterization of the catalysts were obtained and discussed well with XRD, FTIR, SEM, TEM, XPS, DRS and EPR. The visible light induced photocatalytic activities of catalysts were studied by the photocatalytic degradation of MB and ARS.

The following comments should be addressed in order to be evaluated for publication in Catalysts.

1. There is no comparison for the photocatalytic performance of the catalysts with similar articles. Authors should give a comparison in a table in the discussion part to help readers to understand and compare the visible light induced photocatalytic activity of the prepared catalysts.（期刊，）

Response: Thanks a lot for your suggestion. Several photocatalytic performance from the literatures are listed below. It can be seen that the photocatalytic performance in our work is at the intermediate level.

Comparison of the degradation properties of ARS by different catalysts.

Catalyst	Preparation method	Light source	Concentration		Degradation Time (min)/efficiency(%)	Ref.
			Cat. (g/L)	ARS (mg/L)
TiO2		Halogen lamp (>420 nm, 500 W)	1	68	180 / 75	1
ZnO nanoparticles	hydrothermal	UV	1	25	90 / 77	2
Ag/TiO2	wet chemistry method	UV/visible	0.5	20	180 / 80	3
Bi-doped TiO2	sol-gel	Visible Light	0.1	25	90 / 80	4
TiO2/Fe2O3	sol-gel	UV lamp (125 W)		90	120 / 90	5
ZnS/CQDs	chemical precipitation	visible light	0.5	10	250 / 89	6
BiVO4	microwave-assisted combustion synthesis	UV	0.5	100	180 / 99	7
TiO2		UV	0.4	68	200 / 99	8
PP@Au-TiO2		Visible Light	1	20	180 / 80	9
Ce3+/Ce4+/Bi2O3	Solid state reaction	UV–vis	1	20	120 / 78	10
MWCNTs/Si-SH/Pd		UV	0.015	20	150 / 95	11

References:

(1) G. M.Liu, T.W, and J.C. Zhao. Photoassisted Degradation of Dye Pollutants Irreversible Degradation of Alizarin Red under Visible Light Radiation in Air-Equilibrated Aqueous TiO₂ Dispersions. Environ. Sci. Technol. 1999, 33, 2081-2087.

(2) Kansal, S. K.; Lamba, R.; Mehta, S. K.; Umar, A. Photocatalytic degradation of Alizarin Red S using simply synthesized ZnO nanoparticles. Materials Letters 2013, 106, 385-389. DOI: 10.1016/j.matlet.2013.05.074.

(3) de Souza, M. L.; Corio, P. Effect of silver nanoparticles on TiO₂-mediated photodegradation of Alizarin Red S. Applied Catalysis B: Environmental 2013, 136-137, 325-333. DOI: 10.1016/j.apcatb.2013.02.012.

(4) Sood, S.; Mehta, S. K.; Umar, A.; Kansal, S. K. The visible light-driven photocatalytic degradation of Alizarin red S using Bi-doped TiO2 nanoparticles. New J. Chem. 2014, 38 (7), 3127-3136. DOI: 10.1039/c4nj00179f.

(5) Li, F. W. L. M.-s. W. Photocatalytic degradation of Alizarin Ｒed by TiO/Fe2 O3. Applied Chemical Industry 2016, 45 (3), 466-175. DOI: 10.16581/j.cnki.issn1671-3206.20151231.001.

(6) Kaur, S.; Sharma, S.; Kansal, S. K. Synthesis of ZnS/CQDs nanocomposite and its application as a photocatalyst for the degradation of an anionic dye, ARS. Superlattices and Microstructures 2016, 98, 86-95. DOI: 10.1016/j.spmi.2016.08.011.

(7) Abraham, S. D.; David, S. T.; Bennie, R. B.; Joel, C.; Kumar, D. S. Eco-friendly and green synthesis of BiVO4 nanoparticle using microwave irradiation as photocatalayst for the degradation of Alizarin Red S. Journal of Molecular Structure 2016, 1113, 174-181. DOI: 10.1016/j.molstruc.2016.01.053.

(8) Del Giacco, T.; Germani, R.; Saracino, F.; Stradiotto, M. Counterion effect of cationic surfactants on the oxidative degradation of Alizarin Red-S photocatalysed by TiO₂ in aqueous dispersion. Journal of Photochemistry and Photobiology A: Chemistry 2017, 332, 546-553. DOI: 10.1016/j.jphotochem.2016.10.002.

(9) D'Amato, C. A.; Giovannetti, R.; Zannotti, M.; Rommozzi, E.; Ferraro, S.; Seghetti, C.; Minicucci, M.; Gunnella, R.; Di Cicco, A. Enhancement of visible-light photoactivity by polypropylene coated plasmonic Au/TiO₂ for dye degradation in water solution. Applied Surface Science 2018, 441, 575-587. DOI: 10.1016/j.apsusc.2018.01.290.

(10) Akshatha, S.; Sreenivasa, S.; Parashuram, L.; Kumar, V. U.; Sharma, S. C.; Nagabhushana, H.; Kumar, S.; Maiyalagan, T. Synergistic effect of hybrid Ce³⁺/Ce⁴⁺ doped Bi₂O₃ nano-sphere photocatalyst for enhanced photocatalytic degradation of alizarin red S dye and its NUV excited photoluminescence studies. Journal of Environmental Chemical Engineering 2019, 7 (3), 103053. DOI: 10.1016/j.jece.2019.103053.

(11) Veisi, H.; Tatli, S.; Haghgoo, M.; Amisama, A.; Farahmand, S.; Hemmati, S. Immobilization of palladium nanoparticles on thiol-functionalized multi-walled carbon nanotubes with enhanced photocatalytic activity for the degradation of alizarin red. Polyhedron 2019, 165, 9-16. DOI: 10.1016/j.poly.2019.03.002.

 

2. The effect of catalyst amount on the dye degredation should be given according to the experiments. Also the effect of doping amount may be for Ce only should be given.

Response：We thank the reviewer’s comments. Our response to this question is as follows: During the experiment, we investigated the effects of the same metal doping amount (0.1mol) and different element radii on the host perovskite elements. The experimental results showed that Ce doped to A(Na) had the best photocatalytic performance.

3. The XPS core-level spectrum is only given for Ta4f. The other core-level spectra should be given and the deconvolutions and related discussions should be made. Also the percentages of all elements that is obtained by XPS should be given as a Table.

Response：We thank the reviewer’s comments. Our response to this question is as follows: The high-resolution XPS profiles of O 1s and doped metals Fe 2p, Ce 3d, Ni 2p, Mn 2p and Bi 4f were supplemented by Supporting information（Fig.S1 and S2）.

4. The authors only gave the results of reusability experiments for Ce-NTO. It will be better to mention the reusability results of the other catalysts synthesized in the manuscript.

Response：We thank the reviewer’s comments. Our response to this question is as follows: In the process of investigating the reusability of the catalyst, the best catalyst Ce-NTO was selected to investigate its performance.

5. Could the authors please explain how they controlled the temperature of the reaction medium in experimental part?

Response：The photocatalytic degradation experiment was carried out under the magnetic stirring of the photoreaction instrument, and the catalyst was placed under the light source, and the distance between all the beakers and the light source was kept consistent. During the experiment, the cooling circulation pump will be connected to make the reaction at room temperature to avoid the influence of light and heat on the experiment

6. The band gap values of NaTaO3 and Ce-NTO were calculated as different values from DRS and VB-XPS. Could you please explain why these two calculations gave different results?

Response：We thank the reviewer’s comments. Our response to this question is as follows: The UV-Vis diffuse reflectance spectra (DRS) provide a visual representation of the range and extent of the light response of the materials. According to DRS data, the band gap value Eg: (ahν) ²=hν-Eg can be obtained. Valence band (VB) values can be obtained by VB-XPS spectra.

7. There are many grammatical and typing errors in the text and in the figure captions that need to be re-checked and corrected more carefully.

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. We have checked the manuscript in time and have corrected the above errors and made detailed corrections to similar issues in the manuscript.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The goal of the manuscript was to dope NaTaO3 with different elements and to study how doping influence on the structure and photocatalytic degradation of dyes. Photocatalytic degradation experiments have flaws that need to be improved. The authors claim that they corrected it but I do not see that in the manuscript.  Ce-NTO and Ni-NTO for the ARS do not follow the pseudo-first-order kinetic model. Please, remove these two samples from graph 8d), it is confusing to readers, that this is a linear relationship, but is not. The authors need to find which kinetic model is for these two samples, especially because those are the best samples.  According to 8c) Ce and Ni show the same results, and the same photocatalytic behavior, so Ce-NTO is not the best. Also, figure 8 f) which shows the comparison of reaction rate constant k of the samples is not correct, because, for Ni and Ce that do not follow pseudo-first-order reactions, k can not be calculated as it is following. 

Author Response

Response：We would like to thank the reviewers for their valuable comments. As the results shows in Fig 8c, ARS was degraded rapidly within 60 min and tends to be stable during 60-180 min for Ce-NTO and Ni-NTO samples. Based on reviewer's guidelines, we supplemented the degradation experiment for both Ce-NTO and Ni-NTO. The supplementary experiment carried out with the same way as manuscript mentioned. However, the total degradation time last for just 60 min, and analysis every ten minutes. The degradation data were fitted by first-order kinetic for this two samples within 60 min (Fig. R1).

Fig. R1. Photocatalytic degradation ARS reaction kinetic curves

In order to clear the reader's misunderstanding, the Fig. 8 was amended and the corresponding statement has also been revised in the revised manuscript. Fig. 8(b and d) was modified and (f) was deleted. The kinetics curves of ARS were added in the supporting information materials.

Action Taken:

1. Fig. 8 was modified in the revised manuscript as below.

 Figure 8. (a-b) shows the photocatalytic degradation MB curve and primary kinetics; (c) shows the photocatalytic degradation ARS curve

2. Fig. S4 was added in the supporting information materials as below.

Figure S4. Photocatalytic degradation ARS kinetics.(a) all sample within 120 min ,(b) Ce-NTO and Ni-NTO within 60 min

 

3. The statement from line 244 to line 251 in page 9 was modified as follow：“To understand the reaction kinetic behavior of each catalyst for pollutant degradation, the MB and ARS degradation data were further fitted by pseudo primary kinetics. As shown in Figure 8b, the reaction between ln(C/C₀) and light time conforms to qua-si-first-order kinetics:ln(C/C₀) = kt （4-2），k is the apparent reaction rate constant. The histogram shows that the photodegradation rate constant of metal-doped NaTaO₃ is higher than that of the pure phase NaTaO₃. For photocatalytic degradation of ARS, the samples show the different kinetics. Ce-NTO and Ni-NTO sample present the linear fit just within 60 min (As shown in Figure. S4).”

Author Response File: Author Response.pdf

Reviewer 2 Report

The article has undergone a major revision and can be published. The reviewer asks the authors to pay attention once again to comment that can improve the quality of the article:

 

1. In figure 11, the authors show that under the action of light, an electron migrates from trivalent cerium to four valent. However, the CIL data of the non-irradiated sample do not prove this process. Moreover, tetravalent cerium is associated with oxygen in cerium oxide, which is very stable. How cerium atoms/ions +3 and +4 are formed in a solid semiconductor remains a mystery to the reviewer!

Author Response

Response：We would like to thank the reviewers for their valuable comments. Our response to this question is as follows: (1) Doped metal cerium is introduced in the form of nitric acid, and Ce exists in the form of Ce³⁺ in Ce(NO₃)₃•6H₂O；(2) After XPS peak fitting, it can be found that Ce in Ce doped NTO exists in the form of Ce³⁺/Ce⁴⁺ in the catalyst material (3) Metal Ce doped in the form of rod and particle agglomeration around the cubic structure. After local magnification, it was found that the lattice was interlaced, and Ce was agglomerated around the perovskite in the form of CeO₂ after measurement.

Author Response File: Author Response.pdf

Reviewer 4 Report

Most of the comments were addressed in the revised manuscript by the authors. The sentence in page 7 in line 201 should be removed.

Minor editing is required.

Author Response

Response：We would like to thank the reviewers for their valuable comments. We have benefited from the reviewers' careful review, which corrected the errors for us in a timely manner. It has been amended in Page 7, Line 201.

Action taken:

Page 7, Line 201, Delete the sentence "Please improve the writing in this paragraph as it is somehow confusing. "

Author Response File: Author Response.pdf