Three-Dimensional Bi-Enriched Bi2O3/Bi2MoO6 Z-Scheme Heterojunction: Augmented Photocatalytic Phenol Degradation
Round 1
Reviewer 1 Report (Previous Reviewer 1)
Comments and Suggestions for AuthorsThe authors have made many changes to the manuscript, correcting a number of errors. However, the manuscript still needs to be revised. The following comments should be discussed:
(i) The authors described the electrochemical experiment in more detail, but did not answer the question: what radiation source (wavelength, power) was used to measure the photocurrent? Was it the same xenon lamp with a filter as in the photocatalytic experiments or another light source? This information should be added to the text.
(ii) According to Figure S1, the logarithmic dependences of the photodecomposition of phenol Ln(C0/C) on time t are nonlinear. That is, the reaction does not belong to the pseudo-first order and cannot be approximated by equation 2 (Supplementary). Thus, the kinetic rate constants (k) are not determined correctly. These data should be excluded from the manuscript (fig. 6b1,c1,d1 and fig. S1b2,c2,d2 and the corresponding description in the text: section 3.4 and section S3). To interpret the photocatalytic properties, the remaining C0/C time dependences and comparison of the degradation efficiency over 2 h are sufficient.
Author Response
Comments 1 : The authors described the electrochemical experiment in more detail, but did not answer the question: what radiation source (wavelength, power) was used to measure the photocurrent? Was it the same xenon lamp with a filter as in the photocatalytic experiments or another light source? This information should be added to the text.
Response 1: We appreciate the reviewer’s insightful comment. To clarify, identical irradiation conditions were maintained for both electrochemical and photocatalytic experiments. The requested details regarding the radiation source (xenon lamp model: simulate visible light, 300 W Xe lamp and λ > 420 nm) have now been supplemented in Section S2 of the Supporting Information.
The relevant expressions involved in Section S2 have been revised as follows：Photoelectrochemical characters of as-prepared samples were investigated on an electrochemical workstation (CHI660E) with a three-electrode system (simulate visible light, 300 W Xe lamp and λ > 420 nm).
Comments 2: According to Figure S1, the logarithmic dependences of the photodecomposition of phenol Ln(C0/C) on time t are nonlinear. That is, the reaction does not belong to the pseudo-first order and cannot be approximated by equation 2 (Supplementary). Thus, the kinetic rate constants (k) are not determined correctly. These data should be excluded from the manuscript (fig. 6b1,c1,d1 and fig. S1b2,c2,d2 and the corresponding description in the text: section 3.4 and section S3). To interpret the photocatalytic properties, the remaining C0/C time dependences and comparison of the degradation efficiency over 2 h are sufficient.
Response 2: Thank you for your valuable suggestions. In accordance with your recommendations, we have revised the manuscript as follows:
- Supplementary Materials
All panels of Figure S1 and the description related to Equation 2 in Section S3 (which applied to Equation 2 ) have been deleted.
- Main Manuscript
2.1 The revised version of Abstract in the manuscript：Under visible-light irradiation (λ > 420 nm), this heterojunction demonstrated (Bi2O3:Bi2MoO6 = 3:7) exceptional performance, degrading 97.06% of phenol (30 mg/L) within 60 min.
2.2 Figure 6b1, c1, and d1 have been removed, and the corresponding discussion in Section 3.4 has been revised accordingly.
The revised version of Section3.4 now presented in the manuscript：
Figure 6 presents the photocatalytic degradation performance of phenol in simulated wastewater under visible light irradiation using three different photocatalysts. Compared with the photodegradation efficiencies of BBO and BMO, the composite photocatalyst demonstrates significantly enhanced degradation efficiency, achieving nearly complete phenol removal within 60 min as shown in Figure 6a. As illustrated in Figure 6b, the BBO/BMO composite with a mass ratio of 3:7 exhibited optimal photocatalytic performance, achieving 99% degradation efficiency. These results demonstrate that BMO modification with BBO effectively enhances photocatalytic stability and degradation performance [33]. Further experiments were conducted to evaluate the effects of catalyst dosage and initial phenol concentration. For the optimal 3:7 BBO/BMO composite, the optimal catalyst dosage was determined to be 0.1 g (Fig. 6c), and the initial phenol concentration ranging from 10 to 30 mg/L, with 30 mg/L selected as the standard concentration for subsequent experiments (Fig. 6d) (The highest degradation efficiency was observed at 60 min).
Supplementary Explanation：The modified Figure corresponding to Figure 6 in Section 3.4 is detailed in the uploaded file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (Previous Reviewer 2)
Comments and Suggestions for AuthorsThe authors made all the changes
Author Response
Comments : The authors made all the changes.
Response: We express our warm appreciation to the reviewer for acknowledging that all the requested changes have been made，which will greatly motivate our future research endeavors.
Round 2
Reviewer 1 Report (Previous Reviewer 1)
Comments and Suggestions for AuthorsAccept
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have made some corrections to the manuscript, including adding Supporting Information, but the manuscript has not become better. In addition to the illogical presentation, duplications, errors, and incorrect references, there are serious questions about the interpretation of the results. I do not recommend the manuscript for publication.
Here are just some of the comments:
(i). The authors duplicate information from sections "2.2. Synthesis of Photocatalysts" and "2.4.2 Active Species Trapping Experiments" in the main manuscript and in the Supporting Information. The duplicate texts should be removed either in the manuscript or in the Supporting Information.
(ii) It is not clear why all figures from the main manuscript are duplicated in the Supporting Information.
(iii) In section 2.4.1. "Degradation Experiments Detailed materials were provided in S3 (Supporting Information) [14]." It is not clear why a reference to an experiment presented in someone else's work is given here. This is incorrect, the reference in this place should be removed.
(iv) In section 2.4.1 in Supporting Information, the authors state that "The photocatalytic activity of all the samples was conducted by the degradation of Phenol solution under visible light." This is incorrect, since they use a 300 W Xe lamp, which features a rather broad spectrum, including the UV range.
(v) EPR spectroscopy should be added to the title of section 3.1.1.
(vi) The authors stated that they detected the photodegradation of phenol using liquid chromatography, but did not provide any details, and referred to someone else's work [21]. This is incorrect. The experimental conditions should be stated and the reference in this place should be removed.
(vii) The authors used liquid chromatography to determine the photodecomposition of phenol, but did not provide any information on the photoproducts formed. It is not clear what happens to phenol. Without these data, the photocatalytic experiments are of little value.
(viii) The DRS spectra should be moved to Section 3.1, rather than presented in Section 3.3, since they characterize the optical properties of the material.
(ix) The authors' explanations for the presence of narrow peaks related to metallic bismuth in the XRD data are not satisfactory; they do not agree with the modern provisions of X-ray structural analysis.
(x) The article has incorrect reference numbering. References [17]–[45] are not mentioned in the text.
(xi) The authors state that: "The composite catalyst clearly follows an Z-scheme heterojunction mechanism" based on the scheme shown in Figure 6e. This figure of energy levels cannot be a proof of the z-scheme. It is only a confirmation of a type II heterojunction.
(xii) The electrochemical experiment is not described sufficiently. It is not clear under what conditions (wavelength, power) the photocurrent measurements were carried out (Fig. 6f).
(xiii) The description of the luminescence spectra and their influence on the photocatalytic activity is incorrect. There is no data on the excitation wavelength at which the spectra were measured. No spectrum for BBO is provided. The phrase "the gradual attenuation of PL spectra with higher Bi content" is unclear. The authors did not carry out time-resolved measurements to have the ground to talk about the attenuation of the spectra. In addition, the mention of the LSPR raises serious doubts. The SPR band for Bi lies in the UV region, and it is unclear how it affects the luminescence in the visible range of the spectrum.
Reviewer 2 Report
Comments and Suggestions for Authors* Include in the manuscript a statistical analysis of the particle size, for example, a histogram showing the size distribution
* In the EPR analysis, add quantitative data such as the relative intensity between samples or the area under the curve
* In the XPS section, it is stated that the LSPR of metallic Bi is present; include a discussion in the manuscript on how this affects the photocatalytic behavior in relation to the solar spectrum
* Add to the manuscript whether any statistical error or dispersion analysis was performed on the BET surface area and pore volume values
* A good photocatalytic performance is observed for the 3:7 BBO/BMO ratio; it is recommended to include in the manuscript the specific structural or electronic rationale for why this ratio is optimal
* Include negative control data (without light) or control with phenol and light but without catalyst in the scavenger experiments
* The calculation of the rate constant is interesting, but it is recommended to add information about the pseudo-first-order kinetics and its validity in this system
* What level of reproducibility do the degradation experiments have? How many replicates were performed, and what was the standard deviation?
* Add to the manuscript a comparison of the BBO/BMO system with a reference photocatalyst such as P25-TiO₂ or g-C₃N₄
* What was the initial pH of the phenol solutions during the experiments?
* The use of EIS and photocurrent response is solid, but it is recommended to indicate whether the electrodes were prepared with the same catalyst mass or thickness
* Could the observed redshift in DRS also be due to structural defects or vacancies, in addition to the effect of metallic Bi?
* Has the thermal effect of LSPR on charge photogeneration been considered or quantified?
* Include in the manuscript whether the electrochemical stability or interfacial capacitance of the system was measured before and after use to assess its reusability
*Was FTIR analysis performed on the used catalysts after the reaction to evaluate their chemical stability?
