Embedding Thiophene-Amide into g-C3N4 Skeleton with Induction and Delocalization Effects for High Photocatalytic H2 Evolution
Roberto Camposeco
Round 1
Reviewer 1 Report
In the manuscript, the authors constructed thiophene-amide modified g-C3N4, which showed excellent photocatalytic hydrogen production performance when Pt was used as a co-catalyst. This research is fascinating. However, some key issues should be addressed. So I think a major revision is needed.
1、 It can be seen from Figure 1 that after adding EAPC, the weight loss rate in the range of 230-350 °C is slightly smaller than that of pure urea. But the weight loss rate after 380℃ is greater than that of pure urea. Why is that?
2、 Why does the introduction of EAPC cause the reduction of the interlayer spacing, and will this change affect the photocatalytic performance?
3、 In Figure 9, the author obtained the Fermi level of the sample according to the M-S curve. At this time, the Fermi level is relative to the Ag/AgCl electrode. The author should add the corresponding potential of the NHE electrode (pH=6.5) in the manuscript.
4、 The author added chloroplatinic acid to provide a Pt co-catalyst in the hydrogen production experiment, so the system is a g-C3N4/Pt photocatalytic hydrogen production system. However, in the manuscript, only TA-CN and CN materials are introduced. To avoid misunderstandings for readers, the authors need to add Pt as a co-catalyst to participate in the description of photocatalytic hydrogen production. The authors are advised to revise the title to highlight the role of Pt.
5、 The authors must draw a photocatalytic hydrogen production mechanism diagram and a more intuitive reaction catalytic system.
6、 How did the authors confirm that the thiophene amide was successfully intercalated between the heptazine rings rather than directly assembled on top of the heptazine rings?
7、 In the introduction, the authors should add some advantages of photocatalytic technology and applications other than hydrogen production, such as degradation, CO2 reduction, etc. Authors are advised to cite other studies on photocatalysis, such as Liu C, Mao S, Shi M, et al. Chemical Engineering Journal, 2022, 449: 137757; Liu C, Mao S, Shi M, et al. Journal of Hazardous Materials, 2021, 420: 126613; Liu C, Mao S, Wang H, et al. Chemical Engineering Journal, 2022, 430: 132806.
Author Response
Reviewer 1#
In the manuscript, the authors constructed thiophene-amide modified g-C3N4, which showed excellent photocatalytic hydrogen production performance when Pt was used as a co-catalyst. This research is fascinating. However, some key issues should be addressed. So I think a major revision is needed.
- It can be seen from Figure 1 that after adding EAPC, the weight loss rate in the range of 230-350 °C is slightly smaller than that of pure urea. But the weight loss rate after 380 ℃ is greater than that of pure urea. Why is that?
[Response] The result in previous figure could be the testing error. The TG curve of urea was recorded again and the result shows that the weight loss rate of the mixture of EAPC and urea in range of 230-350 °C and 380-600 °C are both slightly lower than that of pure urea. The addition of EAPC reduces the weight loss of the mixture.
- Why does the introduction of EAPC cause the reduction of the interlayer spacing, and will this change affect the photocatalytic performance?
[Response] The intercalation of the thiophene-amide with the groups of C=O, -S- and N-H, which will increase the interaction between the layers by hydrogen bond. Thus, the interlayer spacing reduces. The reduction of interlayer stacking distance is beneficial to the transfer and separate of photogenerated charge carriers between the skeletons, thus the photogenerated electrons migrate more easily to the catalyst surface to participate the catalytic reaction, which will improve the photocatalytic performance.
- In Figure 9, the author obtained the Fermi level of the sample according to the M-S curve. At this time, the Fermi level is relative to the Ag/AgCl electrode. The author should add the corresponding potential of the NHE electrode (pH=6.5) in the manuscript.
[Response] The potentials in Fig. 9 were revised to the corresponding potentials of NHE (pH=6.5) accordingly.
- The author added chloroplatinic acid to provide a Pt co-catalyst in the hydrogen production experiment, so the system is a g-C3N4/Pt photocatalytic hydrogen production system. However, in the manuscript, only TA-CN and CN materials are introduced. To avoid misunderstandings for readers, the authors need to add Pt as a co-catalyst to participate in the description of photocatalytic hydrogen production. The authors are advised to revise the title to highlight the role of Pt.
[Response] In this study, Pt was used as a co-catalyst for all the catalytic generation of hydrogen, which is indicated in the experimental section (Section 3.5). We have revised accordingly.
- The authors must draw a photocatalytic hydrogen production mechanism diagram and a more intuitive reaction catalytic system.
[Response] The possible mechanism of photocatalytic hydrogen production was added in the revised manuscript (Fig. 12), and the catalytic reaction process is also elaborated (Line 1-7, Page 13).
- How did the authors confirm that the thiophene amide was successfully intercalated between the heptazine rings rather than directly assembled on top of the heptazine rings?
[Response] Firstly, as indicated in the TG curve (Fig. 1), the mixture of urea and EAPC experiences an additional weight loss between 231 ℃ and 255 ℃, corresponding to the reaction process of the amino and ester groups of EAPC with urea, meaning that EAPC was involved in the step-by-step polycondensation of urea. In addition, FT-IR (Fig. 3) and NMR (Fig. 5) also demonstrate the attachment of heptazine rings.
- In the introduction, the authors should add some advantages of photocatalytic technology and applications other than hydrogen production, such as degradation, CO2 reduction, etc. Authors are advised to cite other studies on photocatalysis, such as Liu C, Mao S, Shi M, et al. Chemical Engineering Journal, 2022, 449: 137757; Liu C, Mao S, Shi M, et al. Journal of Hazardous Materials, 2021, 420: 126613; Liu C, Mao S, Wang H, et al. Chemical
[Response] The related references were added accordingly (Ref. [1-4]).
Reviewer 2 Report
Comments Catalysts-1889791
This work reports the H2 evolution by using g-C3N4 material with different quantities of EAPC of 5, 10, 15, and 20 mg. In general, the paper is well organized. Although the authors used many types of characterizations to study the targeted materials, the discussion of the paper lacks findings. Some observations are as follows:
1. What the main reason of calcined at 550°C add the amount of flux used during calcination, the authors performed further experiments to find the optimal temperature, in addition, the authors use 50 mg suspended in 100 mL, the authors carried out tests with other amounts of material explain?
2. In XRD the authors must mention the JCPDS on which they are based, In addition, the authors mention that there is a shift to higher angles owing to the reduction of the interlayer stacking distance what is the value of the distance?
3. The addition of TA-CN-x enhances the photocatalytic H2 production under UV or visible irradiation. The explanations for enhancement effect are unclear in fact in several of the characterizations not much difference between CN and TA-CN-2 is seen as in XPS C 1s, N 1s and O1s and FTIR the spectra and values presented in table 1 are very similar, in fact where more differences were observed was in the electrochemical characterization the authors should give a deeper discussion.
4. In figure 11 a authors should present the value of photolysis.
5. How much does on the hydrogen production the addition of 3 mL of H2PtCl6 6H2O as co-catalyst explain?
Author Response
Reviewer 2#
This work reports the H2 evolution by using g-C3N4 material with different quantities of EAPC of 5, 10, 15, and 20 mg. In general, the paper is well organized. Although the authors used many types of characterizations to study the targeted materials, the discussion of the paper lacks findings. Some observations are as follows:
- What the main reason of calcined at 550°C add the amount of flux used during calcination, the authors performed further experiments to find the optimal temperature, in addition, the authors use 50 mg suspended in 100 mL, the authors carried out tests with other amounts of material explain?
[Response] According to the reported and our previous experiments, the preparation of CN using urea as a precursor at 550 °C will produce the product with high surface area and thus high photocatalytic activity for hydrogen generation. And the amount of 50 mg catalyst is also reported in many papers. The comparison of the performance of the catalysts prepared in this study with others will be reasonable.
- In XRD the authors must mention the JCPDS on which they are based. In addition, the authors mention that there is a shift to higher angles owing to the reduction of the interlayer stacking distance what is the value of the distance?
[Response] The XRD pattern of CN shows two obvious diffraction peaks, which has been confirmed by a large number of studies.
The value of the layer distance can be calculated according to Bragg Equation: 2dsinθ = nλ. The average distance can be obtained after calculation (0.16682 nm for CN and 0.16554 for TA-CN-2).
- The addition of TA-CN-x enhances the photocatalytic H2 production under UV or visible irradiation. The explanations for enhancement effect are unclear in fact in several of the characterizations not much difference between CN and TA-CN-2 is seen as in XPS C 1s, N 1s and O1s and FTIR the spectra and values presented in table 1 are very similar, in fact where more differences were observed was in the electrochemical characterization the authors should give a deeper discussion.
[Response] In this study, some techniques such as XRD, FTIR and NMR are used to characterize the structure of the prepared catalysts, while others including UV-Vis, PL, TR-PL, theoretical calculation and electrochemical characterization are adopted to disclose the mechanism of the enhanced photocatalytic performance of the catalysts. The stronger visible light absorption and higher separation and higher migration efficiency of photogenerated carriers of catalyst TA-CN facilitate the improvement of the modified catalyst with higher hydrogen production activity.
- In figure 11a authors should present the value of photolysis.
[Response] The amounts of catalysts used in the experiment were supplemented in the title of the Fig. 11a, and other experimental conditions are described in Section 3.5.
- How much does on the hydrogen production the addition of 3 mL of H2PtCl6·6H2O as co-catalyst explain?
[Response] In this study, Pt was used as a co-catalyst for all the catalytic generation of hydrogen, which is indicated in the experimental section (Section 3.5).
Round 2
Reviewer 1 Report
The authors have made the necessary revisions and I think the current manuscript is acceptable.
Author Response
Thank you very much.
Reviewer 2 Report
The authors have made and responded to all the questions taking references from previous works. The authors should provide clearer scale bars for the HRTEM images.
Author Response
The scale bars in all SEM and TEM images are revised accordingly (Figure 6).
