Promotion Effect of the Keggin Structure on the Sulfur and Water Resistance of Pt/CeTi Catalysts for CO Oxidation
Round 1
Reviewer 1 Report
Authors describe the influence of a Keggin structure POM (before and after a strong thermal treatment) once included in Cerium Titanium composite oxide.
The materials have been characterized by different methods. Those materials have been used in order to oxidize CO. The idea is to add POM in order to make the catalytic material more stable towards SO2 poisoning and water. The authors show the presence of Keggin does contribute to a stability of the catalytic activity mainly in presence of SO2, H2O being less disturbing. But once Keggin is calcinted, the activity is not good.
Some parts need to be corrected before being publishable.
First is the experimental part. The synthetic part is not very easy to understand. The quantities must be exactly indicated to be reproducible.
The characterization of the catalytic materials should be indicated before the catalytic tests.
Table 1 should be not only commented but the reason of the values should be given. Why is the system with POM with higher pores ?
Fig. 1 : x axis temperature. Keep same style on all the graphs.
Fig. 6 : Are the values normalized ? It is not explained, especially because intensity is in arbitrary units.
The explanation of the low activity of the "not Keggin" is not clear.
This should be explained deeper.
A fundamental question is the number of samples of each material that has been tested and the number of reactions that have been repeated. Although the materials were followed during long period, those tests should be duplicated (or tripicated) to ensure reproducibility of the tests.
Author Response
Comments:
Authors describe the influence of a Keggin structure POM (before and after a strong thermal treatment) once included in Cerium Titanium composite oxide.
The materials have been characterized by different methods. Those materials have been used in order to oxidize CO. The idea is to add POM in order to make the catalytic material more stable towards SO2 poisoning and water. The authors show the presence of Keggin does contribute to a stability of the catalytic activity mainly in presence of SO2, H2O being less disturbing. But once Keggin is calcinted, the activity is not good.
Some parts need to be corrected before being publishable.
- First is the experimental part. The synthetic part is not very easy to understand. The quantities must be exactly indicated to be reproducible.
Answers: We have revised the experimental part according to the reviewer’s suggestion.
- The characterization of the catalytic materials should be indicated before the catalytic tests.
Answers: The authors thought that putting the characterization results of the catalytic materials in the back of catalytic tests was convenient for discussion the relationship of catalyst structure and catalytic activity.
- Table 1 should be not only commented but the reason of the values should be given. Why is the system with POM with higher pores ?
Answers: We have revised the manuscript according to the reviewer’s suggestion, see page 5.
- 1 : x axis temperature. Keep same style on all the graphs.
Answers: Fig.1 has been revised according to the reviewer’s suggestion.
Fig. 6 : Are the values normalized ? It is not explained, especially because intensity is in arbitrary units.
Answers: Fig.6 has been revised according to the reviewer’s suggestion. The right axe scale has been added.
The explanation of the low activity of the "not Keggin" is not clear. This should be explained deeper.
Answers: We have revised the corresponding statement in the manuscript.
A fundamental question is the number of samples of each material that has been tested and the number of reactions that have been repeated. Although the materials were followed during long period, those tests should be duplicated (or tripicated) to ensure reproducibility of the tests.
Answers: This is a good question for the material preparation. In fact, every catalyst had been prepared and tested for several time, demonstrating the reproducibility of the preparation method and performance.
Reviewer 2 Report
This paper describes CO oxidation over Pt catalyst in the presence of catalyst poisoning, SO2. The catalysts were characterized well using SEM, TEM, XPS, TPD and so on. It seems that the paper is basically written well. However, following two points as listed below were not discussed well. To understand the paper well, the authors should discuss the two points.
1) Main topic of this paper is related to carbon (carbon monoxide or CO2). However, the data about carbon-containing products are very limited; the amount of CO in the gas phase was only measured. More data about carbon-containing products are necessary for better understanding of the contents in the paper. Carbon on the catalysts should be characterized by using surface analytical instruments such as XPS.
2) Pt was used as a catalyst in this study. The XPS data suggested that valence states of Pt in this study were +2 and +4. Generally, in some reactions metallic Pt shows higher activity than Pt2+ or Pt4+ containing catalysts. So, the authors should measure the catalytic activity of metallic Pt with the valence state of 0.
Author Response
Comments:
This paper describes CO oxidation over Pt catalyst in the presence of catalyst poisoning, SO2. The catalysts were characterized well using SEM, TEM, XPS, TPD and so on. It seems that the paper is basically written well. However, following two points as listed below were not discussed well. To understand the paper well, the authors should discuss the two points.
1) Main topic of this paper is related to carbon (carbon monoxide or CO2). However, the data about carbon-containing products are very limited; the amount of CO in the gas phase was only measured. More data about carbon-containing products are necessary for better understanding of the contents in the paper. Carbon on the catalysts should be characterized by using surface analytical instruments such as XPS.
Answers: The product of CO oxidation over the catalysts was only CO2 and there were few or no carbonate species on the catalysts surface, see Figure S4.
2) Pt was used as a catalyst in this study. The XPS data suggested that valence states of Pt in this study were +2 and +4. Generally, in some reactions metallic Pt shows higher activity than Pt2+ or Pt4+ containing catalysts. So, the authors should measure the catalytic activity of metallic Pt with the valence state of 0.
Answers: We added the XPS spectra of Pt 4f in the recovered Pt/CeTi, Pt/Keg-CeTi and Pt/MoP-CeTi catalysts (Figure S2). It could be seen that there were certain amounts of Pt0 formed during the CO oxidation reaction different from the fresh ones.
Round 2
Reviewer 1 Report
Authors answered to some questions.
The last answer about the number of experiments is not convincing.
It is scientifically impossible to believe that experiments done with different samples (although under the same experimental conditions) will give identical results. What is the exact number of samples ? What is the margin of errors ? This has to be strongly specified and justified by giving proofs in SI
Fig; 1 : x axis title is mistyped. (temperture)
Author Response
Answers to Comments by Referees
Reviewer 1
Comments:
The last answer about the number of experiments is not convincing.
It is scientifically impossible to believe that experiments done with different samples (although under the same experimental conditions) will give identical results. What is the exact number of samples ? What is the margin of errors ? This has to be strongly specified and justified by giving proofs in SI.
Answers: We have added the activity data of the three parallel samples of Pt/CeTi, Pt/Keg-CeTi and Pt/MoP-CeTi in the supporting information (Figure S5).
Fig; 1 : x axis title is mistyped. (temperture)
Answers: We have revised the figure 1. I am awfully sorry for a so stupid mistake.
Round 3
Reviewer 1 Report
Authors answered to all questions.
