Recent Progress of Metal-Oxide-Based Catalysts for Non-Oxidative Coupling of Methane to Ethane and Hydrogen
, Yaolin Chen 1,2, Fang Wang 2 and Ying Zhou 1,2,*
Round 1
Reviewer 1 Report
Please see the attachment.
Comments for author File: 
Comments.pdf
Author Response
Thank you for your precious comment. We have adjusted the number and content of Figures 1 to 6 based on the suggestions of the reviewer. The correction figures were highlighted in yellow on the caption. Additionally, we have reviewed the full of text and corrected some spelling and grammar errors that occurred. The corrected texts were added to line 31-32, line 111, line 118-119, line 194, line 206 line 208, line 212-213, line 225, line 241, line 251, line 258 (highlighted in blue).Reviewer 2 Report
1. The manuscript should be extensively proofread. For example, the following sentence in the abstract has no meaning:
“Directly conversion of methane into higher value chemicals, which has significant advantages to adapt to the development of green and sustainable chemicals.”
2. The nomenclature of the chemicals’ names should be adjusted. Rather methane or CH4 etc. should be used
3. Several works on the photocatalysis should be discussed https://doi.org/10.1016/j.apenergy.2022.119461, https://doi.org/10.1039/D2NR01489K
4. The review also looks outdated as only standard thermal and photocatalytic materials, such as metals and metal oxides are discussed. I suggest every section should be extended and a comprehensive review on the application of various novel nanomaterials and two-dimensional structures in thermal catalysis and photocatalysis should be added. See
https://doi.org/10.1088/0957-4484/22/38/385502 https://doi.org/10.1021/acsnano.1c00627
https://doi.org/10.1016/j.envres.2022.114699 https://doi.org/10.3390/solar2020017 https://doi.org/10.3390/molecules28062495 https://doi.org/10.3390/catal12121549
5. There are 3 general suggestions for creating a photocatalyst for the methane non-oxidation coupling reaction in Conclusions. Every suggestion must be clarified. Specific actions for developing in situ technology to explore the structural changes of intermediates and catalysts or for the use of sunlight of different wavebands should be suggested.
Author Response
2.1 The manuscript should be extensively proofread. For example, the following sentence in the abstract has no meaning: “Directly conversion of methane into higher value chemicals, which has significant advantages to adapt to the development of green and sustainable chemicals.”
Response 2.1: Thank you for your precious comment. We have re-written this part in the abstract, such as “Direct conversion of methane into high value-added chemicals has important scientific significance and broad commercial prospects for the efficient utilization of methane resources.” The explanatory texts were added to page 1: line 12-13 (highlighted in blue).
2.2. The nomenclature of the chemicals’ names should be adjusted. Rather methane or CH4 etc. should be used.
Response 2.2: Thanks for your suggestion. The main component of natural gas is methane, and the abbreviation for it is CH4, so in the text “methane or CH4” is used. Therefore, we have reviewed and unified the abbreviation chemicals' names for the full text. The descriptions of hydrogen, methane, and ethane in the text have been abbreviated unless they appear for the first time.
2.3. Several works on the photocatalysis should be discussed, https://doi.org/10.1016/j.apenergy.2022.119461, https://doi.org/10.1039/D2NR01489K.
Response 2.3: We sincerely appreciate the suggestion. Although this review compares various catalysts used under thermal or photocatalytic conditions, it mainly summarizes some catalysts used in the conversion of methane to ethane and hydrogen. The photocatalysts by the literatures (10.1016/j.apenergy.2022.119461 and 10.1039/D2NR01489K) are used in photocatalysis photocatalytic water splitting and photocatalytic hydrogen evolution. Although photocatalysts are suitable for different photocatalytic reactions, they have some common characteristics. Therefore, we have added the above literature suggested by the reviewer to further illustrate the advantages of metal-modified catalysts in redox reactions. The explanatory texts were on line 228-230 and 232-233 (highlighted in blue).
2.4. The review also looks outdated as only standard thermal and photocatalytic materials, such as metals and metal oxides are discussed. I suggest every section should be extended and a comprehensive review on the application of various novel nanomaterials and two-dimensional structures in thermal catalysis and photocatalysis should be added. See https://doi.org/10.1088/0957-4484/22/38/385502, https://doi.org/10.1021/acsnano.1c00627,https://doi.org/10.1016/j.envres.2022.114699, https://doi.org/10.3390/solar2020017, https://doi.org/10.3390/molecules28062495,
https://doi.org/10.3390/catal12121549.
Response 2.4: Thanks for your suggestion. Although this review compares various catalysts used under thermal or photocatalytic conditions, it mainly summarizes some metal oxide based catalysts used in the conversion of methane to ethane and hydrogen. The main reason is that metal and metal oxide catalysts are the most studied catalysts in the reaction of non-oxidative coupling of methane, and it is also hoped to focus more on the development of this type of catalyst. Therefore, this review does not study the application of the remaining two-dimensional structure catalysts in thermal catalysis and photocatalysis. Considering the content of the review, we have made some restrictive modifications to the title, changing the "catalysts" into "metal oxide based catalysts".
2.5. There are 3 general suggestions for creating a photocatalyst for the methane non-oxidation coupling reaction in Conclusions. Every suggestion must be clarified. Specific actions for developing in situ technology to explore the structural changes of intermediates and catalysts or for the use of sunlight of different wavebands should be suggested.
Response 2.5: We sincerely appreciate the suggestion. In light of the above discussion, we propose the following methods for creating a photocatalyst for the NOCM reaction, (1) Developing in situ technology, such as in-situ X-ray Absorption Fine Structure (XAFS), in-situ X-ray photoelectron spectroscopy (XPS), and in-situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), to explore the structural changes of intermediates and catalysts in an ultra-short time scale, which is helpful to further distinguish the thermal catalytic effect and photocatalytic effect. (2) The laboratory usually uses the Xe lamp as the solar energy source and has limited use of sunlight of different wavebands. It needs to continue to expand the efficiency of solar energy conversion and utilization. If researchers can try to use solar simulators for indoor testing, or use solar concentrators to directly convert and utilize solar energy, it will be beneficial to large-scale application research of solar energy. (3) More research can focus on bimetallic catalysts to improve the selectivity of C2H6 by using the synergistic effect of different metals. It is necessary to further clarify the reaction mechanism of the cocatalysts. The explanatory texts were on line 361-363, and 367-370 (highlighted in blue).
Round 2
Reviewer 2 Report
The quality of the manuscript is now suitable for its acceptance.
