Nano-Sheets of CsNiVF6 Pyrochlore Electrocatalyst for Enhanced Urea Oxidation and Hydrogen Green Production Reactions
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this work, the authors prepare nano-sheet pyrochlore-type CsNiVF6 electrocatalyst for efficient urea oxidation and hydrogen production. Various electrochemical measurements and characterizations demonstrate the origins of this material. Some important issues must be solved before acceptance.
1. The unit of mass activity is wrong, which should be mA mg-1. Also, please replace “/” with “-1” for the units through the manuscript. The reference of PDF card should be provided.
2. To highlight the importance of green hydrogen production and improve the readability of the manuscript, the authors should combine some data in the introduction part. Please refer to 10.1039/D3EE02695G for this point.
3. Please clearly identify the elements for the atoms with different colors. The scale bars of Figure 2, 3 and 7 are too small.
4. The necessary references to support the XPS analysis should be given. In Figure 4a, we can clearly observe the signal of O 1s. The detailed oxygen species of material are important for OER. Please fit and analyze the O 1s data, which can refer to this work 10.1002/cey2.465.
Comments on the Quality of English Language
Minor editing of English language required
Author Response
Reviewer #1
In this work, the authors prepare nano-sheet pyrochlore-type CsNiVF6 electrocatalyst for efficient urea oxidation and hydrogen production. Various electrochemical measurements and characterizations demonstrate the origins of this material. Some important issues must be solved before acceptance.
1:-The unit of mass activity is wrong, which should be mA mg-1. Also, please replace “/” with “-1” for the units throughout the manuscript. The reference of PDF card should be provided.
Reply: We acknowledge the need for correction in the unit of mass activity. We made the necessary amendments to (mA mg-1) and highlighted as suggested However, the change of mass activity to mA mg-1, should not affect the reported values because the geometric area of our electrode was fixed at 1.0 cm2. Additionally, the reference to the PDF card is added and highlighted in the appropriate section.
2- To highlight the importance of green hydrogen production and improve the readability of the manuscript, the authors should combine some data in the introduction part. Please refer to 10.1039/D3EE02695G for this point.
Reply: Many thanks for the suggestion, in the introduction, we integrated the relevant information and cited the above-mentioned work in reference [7].
3-Please clearly identify the elements for the atoms with different colors. The scale bars of Figure 2, 3 and 7 are too small.
Reply: These issues are addressed, the image colour in Fig. 3c has been changed and the scale bars are adjusted for better visibility.
4- The necessary references to support the XPS analysis should be given. In Figure 4a, we can clearly observe the signal of O 1s. The detailed oxygen species of material are important for OER. Please fit and analyze the O 1s data, which can refer to this work 10.1002/cey2.465.
Reply: We appreciate this suggestion, the required references to support the XPS analysis are added on page 5. The O 1s signal analysis was performed and added in Fig. 4f with relevant cited supporting references.
Reviewer 2 Report
Comments and Suggestions for AuthorsIn this manuscript, the authors reported the successful synthesis of caesium nickel vanadium fluoride (CsNiVF6) pyrochlore nano-sheet catalyst via solid-phase synthesis and its electrochemical performance for green hydrogen production through urea electrolysis in alkaline media. Overall, this work reported a novel catalyst that can be utilized for efficient hydrogen production from urea electrolysis. The manuscript was generally well organized. I think this manuscript suits the readership of the journal Catalysts. However, to further enhance the quality of the manuscript, the below detailed comments need to be properly addressed.
1. Is it common to report the mass activity in “mA/cm2 mg”? Usually it should be “mA/mg”. Please double check with other literature.
2. Recent works on OER electrocatalysis can be included in Introduction (e.g., Small Methods, 2022, 6, 2201099).
3. Figure1a, for the XRD data analysis, in addition to the peaks already identified, there appear to be some other peaks that were not identified. What material structures/phases do they refer to?
4. Figure 1b, when displaying a schematic of the pyrochlore structure, the zone axis (a,b,c zone or x,y,z zone) should be specified. The color label for each sphere should also be specified.
5. In the Introduction, related works on perovskite materials (Mater. Horiz., 2020, 7, 2519) are recommended to be referenced.
6. Figure 5b, the legend is missing the unit of the mass (ug). Figure 5d inset, visibility should be enhanced.
7. To appeal to a broader readership, works on urea electrolysis can be referenced (e.g., Journal of Colloid and Interface Science 2024, 661, 629-661).
8. Figure 6a and its inset, the y axis should be revised from Z’’ to –Z’’. A negative sign is missing.
9. Based on Figure 6b, I wouldn’t call the sample is stable. There is obvious drop of current density during the 3-hr test. Maybe the authors should not highlight the stability, but rather objectively describe the observed activity change with time due to likely leaching of Cs, etc.
Author Response
Reviewer #2
In this manuscript, the authors reported the successful synthesis of caesium nickel vanadium fluoride (CsNiVF6) pyrochlore nano-sheet catalyst via solid-phase synthesis and its electrochemical performance for green hydrogen production through urea electrolysis in alkaline media. Overall, this work reported a novel catalyst that can be utilized for efficient hydrogen production from urea electrolysis. The manuscript was generally well organized. I think this manuscript suits the readership of the journal Catalysts. However, to further enhance the quality of the manuscript, the below detailed comments need to be properly addressed.
Comment 1: Is it common to report the mass activity in “mA/cm2 mg”? Usually it should be “mA/mg”. Please double check with other literature.
Reply: in compliance with this comment, the mass activity unit is updated as “mA mg-1” throughout the whole text.
Comment 2: Recent works on OER electrocatalysis can be included in Introduction (e.g., Small Methods, 2022, 6, 2201099).
Reply: The above-mentioned work of perovskite catalysts is highlighted in the introduction section on page 2, and cited in reference [54].
Comment 3: Figure1a, for the XRD data analysis, in addition to the peaks already identified, there appear to be some other peaks that were not identified. What material structures/phases do they refer to?
Reply: the XRD result in Figure 1a is re-examined and the unidentified peaks in the XRD pattern seem to originate from minor residual impurities from the starting fluoride precursors that can be effectively removed using deionized water. The text is amended on page 4 to clarify this point.
Comment 4: Figure 1b, when displaying a schematic of the pyrochlore structure, the zone axis (a,b,c zone or x,y,z zone) should be specified. The color label for each sphere should also be specified.
Reply: Figure 1b is updated with the zone axis and color label information for the structure is added and specified for clarity.
Comment 5: In the Introduction, related works on perovskite materials (Mater. Horiz., 2020, 7, 2519) are recommended to be referenced.
Reply: The suggested work of perovskite materials (Mater. Horiz., 2020, 7, 2519) is noted and cited as a reference [37].
Comment 6: Figure 5b, the legend is missing the unit of the mass (ug). Figure 5d inset, visibility should be enhanced.
Reply: Figure 5b legend is updated and the visibility of the inset in Fig. 5d is enhanced.
Comment 7: To appeal to a broader readership, works on urea electrolysis can be referenced (e.g., Journal of Colloid and Interface Science 2024, 661, 629-661).
Reply: Thank you for the suggestion, the above-mentioned work on urea electrolysis is cited in the introduction as a reference [25].
Comment 8: Figure 6a and its inset, the y axis should be revised from Z’’ to –Z’’. A negative sign is missing.
Reply: The y-axis label in Figure 6a is corrected as per your suggestion, and the missing negative sign is included.
Comment 9: Based on Figure 6b, I wouldn’t call the sample is stable. There is obvious drop of current density during the 3-hr test. Maybe the authors should not highlight the stability, but rather objectively describe the observed activity change with time due to likely leaching of Cs, etc.
Reply: the observation regarding the sample stability in Figure 6b is acknowledged and proper description of the current/time behavior description is provided and highlighted on page 8.
