Intentionally Incorporated Fe Cations in Silverton Polyoxometalates Forming Fenton-like Photocatalysts for Enhanced Degradation

Round 1

Reviewer 1 Report

The authors presented an introductory study for preparing iron-doped POM to enhance photocatalytic activity. 

The manuscript was written well, but it still needs significant revision for 

1. Experimental part, the authors should mention the correct full name before abbreviations such as SSA, Rh B dye [Rhodamine B (RhB)].

2. the authors should mention all procedures for the preparation of precursors (Main sphere CoWOH) that used in the manuscript for comparison with FeCoWOH 

2. the authors compare the photodegradation activity between several active materials (Figure 7), but the authors do not discuss it well, although this is the main application (no discussion about 7c). 

 

Author Response

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Reviewer 2 Report

In this wok, the Fe ion incorporated Co4W6O21(OH)2·4H2O sphere network was synthesized and used in the photocatalytic degradation of RhB. The paper has been well-written, and I think it can be interesting for readers. But there are a few issues that must be addressed and can be accepted after a minor revision. Please see the comments:

 

-The abstract must be more informative and quantitative

-Lines 60-65: results shouldn’t be reported in the introduction

-Literature review must be improved

-The source and purity of chemicals must be added.

-The adsorption effects of photocatalysts are omitted in Fig. 7. What is the adsorption behavior in dark places?

-Mechanism of degradation should be illustrated in a schematic in the presence and absence of hydrogen peroxide.

-What is the role of redox properties of POM in the degradation process?

-What is the role of the redox property of POM (as a main characteristic of POM (Gold Bulletin 45, 145-151, Chemosphere 281, 130795) in degradation of dye?

-Experimental condition must be added to the figure caption s

-What is the effect of the H2O2 amount?

-How much is the leaching of photocatalysts?

-Is the photocatalyst reusable?

Author Response

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Author Response File: Author Response.doc

Reviewer 3 Report

In this manuscript, Dong and co-workers investigated the photocatalytic degradation of Rhodamine B (RhB) over a Fe_xCo_4-xWOH catalyst. The authors demonstrated that partially replacing of Co atoms to Fe played a critical role in modulating the electron state, band structure and photocatalytic activity. Despite the fact that the modification method and material are interesting, I would not recommend the paper for publication. Specific issues are following:

1. The journal scope involves a comprehensive investigation of the materials surface and its effect on the perfomances in various applications. For instance, in this paper, nitrogen adsorption-desorption isotherms are presented, but there is a lack of their discussion. Moreover, it is necessary to explain how the physicochemical properties (morphology, BET surface area, etc.) affect the photocatalytic activity. The authors in Section 3.2 simply described the results and did not explain the effect in terms of surface science.

2. Continuing the discussion of BET surface area, it almost doubled after the modification with Fe. It is known that an increase in the BET surface area not only increases the photocatalytic activity due to a larger number of active sites, but also often leads to a larger adsorption capacity. In general, the authors did not provide the data on the adsorption capacity. It is recommended to investigate and explain.

3. The authors should give the wavelength range of a Xe lamp used. It is well-known that the Xe lamps includes broad-spectrum wavelengths from 100 to 1100 nm. If the authors used a filter (λ > 420 nm), it is necessary to indicate this.

4. I am not sure that it is correct to compare your results with the activity of TiO₂ (Figure 7(b)) because titanium dioxide is active only in UV light. At the same time, in the whole text, the authors claim that they investigated the visible-light photocatalytic degradation of RhB. It is more correct to give a comparative table, which will show the activity of your material with those already studied and similar in structure.

5. It is highly recommended to study kinetics as well. Moreover, the calculation of the TON and TOF values with the following comparison is also recommended.

6. The autfors should provide whether the catalyst changes after the reaction (e.g., SEM and XRD data). To demonstrate the stability of the photocatalyst, the test data of the recycling experiments should be provided.

7. The authors claim that the replacing of Co atoms to Fe changes the band structure. But I did not find the energy diagrams with the indication of the valance and conduction band positions. This is an extremely important aspect in the study of new materials for photocatalysis.

I hope my comments help you to improve the manuscript.

Minor editing of English language is required.

Author Response

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Author Response File: Author Response.doc

Round 2

Reviewer 3 Report

The authors have revised the manuscript carefully. Acceptance in the current form is recommended.

Minor editing is required.