Effect of NaOH Concentration on Rapidly Quenched Cu–Al Alloy-Derived Cu Catalyst for CO2 Hydrogenation to CH3OH
, Minghua Qiao 1,*, Xiaoxin Zhang 2 and Baoning Zong 2,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsTwo significant challenges have emerged in recent years: climate change and the depletion of fossil fuels. The reduction of greenhouse gas emissions into the atmosphere and the identification of alternative sources of carbon for the production of energy and chemicals have therefore become pressing challenges. The development of processes to convert CO2, one of the greenhouse gases, into valuable chemicals represents a potential solution to both problems. Consequently, the global search for catalysts for CO2 utilization is intensifying. Methanol is a particularly promising candidate for conversion into valuable chemicals due to its versatility. It can be employed as a raw material for the production of a number of fine chemicals, as a fuel additive and as an energy carrier.
From this perspective, the significance of this study is considerable.
This manuscript examines the effect of NaOH concentration on the performance of a rapidly quenched Cu–Al alloy-derived Cu catalyst for CO2 hydrogenation to CH3OH.
The manuscript is well structured and easy to read. However, there are a few points that could benefit from further clarification.
1) Page 4: Due to the relatively low content of Al and the overlapping of the Al 2p peak with the Cu 3p peak, the analysis of the Al 2p spectra is not preformed.
Looks like there's a typo here.
2) Page 5: As summarized in Table 2, the surface Cu2+ content among all the Cu species is about 2.6% on RQ Cu-10. The surface Cu+ content on RQ Cu-3 is 26.7%, which is comparable to that on RQ Cu-10.
It appears from the table that the value is 26.4, not 2.6. Or have I misunderstood?
3) Page 7: According to Table 4, the CO2 conversion increases first, maximizes at 473 K, and then decreases at higher temperatures.
It is necessary to ascertain the nature of this phenomenon and provide an explanation.
4) Page 8: In contrast, the SBET and Vpore of the RQ Cu-3 catalyst are well preserved or even slightly increase after reaction, and its SCu also increases. The SCu/SBET ratio of the RQ Cu-3 catalyst also increases markedly from 31% before reaction to 42% after reaction.
Please be aware that this is a factual statement. It is necessary to explain the reasons behind these changes.
5) In order to provide a comprehensive overview of the subject matter, it is recommended that the list of references be expanded to include more recent works on the topic.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsHere are some comments on the article titled "Effect of NaOH concentration on rapidly quenched Cu–Al alloy-derived Cu catalyst for CO2 hydrogenation to CH3OH":
1) Minor improvements in language for the clarity of certain sections could enhance the overall readability for a broader audience.
2) The study only examined the effect of NaOH concentration (3 wt% vs 10 wt%) on the properties and catalytic performance of the rapidly quenched Cu catalysts. Other parameters that could impact the catalyst properties and performance, such as leaching time, temperature, etc. were not investigated.
3) The catalytic performance was only evaluated for CO2 hydrogenation to methanol at a limited number of reaction temperatures (453-513 K) and pressures (3-5 MPa). A more comprehensive evaluation of the catalyst's performance over a broader range of reaction conditions would provide a better understanding of the catalyst's capabilities.
4) While the article discusses the effects of residual Al species on catalytic performance, it lacks detailed mechanistic investigations to support these claims. Further studies, such as in-situ characterization during the reaction, could provide more evidence for the proposed stabilizing role of Al.
5) The article relies on a limited set of characterization techniques, such as XRD, XPS, and SEM-EDX. Employing additional techniques, like H2 chemisorption or in-situ FTIR, could provide more comprehensive insights into the catalyst structure, active sites, and reaction mechanism.
6) The study only focused on CO2 hydrogenation to methanol and did not explore the potential of these rapidly quenched Cu catalysts for other catalytic applications, which could be an interesting area for future research.
7) The study only compares the performance of the RQ Cu catalysts with the commercial Cu/ZnO/Al2O3 catalyst. Comparing the RQ Cu catalysts with other recently reported Cu-based catalysts for CO2 hydrogenation would help to better evaluate their performance and novelty.
By the way, the study provides valuable insights into the impact of NaOH concentration on the properties of and performance of the rapidly quenched Cu catalysts, further research is needed to fully understand the structure-activity relationships and optimize the catalyst design for practical CO2 hydrogenation applications.
Comments on the Quality of English LanguageMinor improvements in language for the clarity of certain sections could enhance the overall readability for a broader audience.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have correctly responded to most of the reviewers’ comments. Therefore, it can be accepted for publication in its current form.
