Review Reports

Round 1

Reviewer 1 Report

This paper reports Kinetic Behavior of Fabricated CuO/ZrO2 Oxygen Carriers for Chemical Looping Oxygen Uncoupling. The research and the report are well prepared. Few comments below can be considered as inputs to enhance the manuscript quality.

• Provide the background of the reseach in the abstract. Why the research is important?
• Please state clearly the research gap/novelty of the study in the introduction. It is still unclear currently.
• Line84-86: what is the basis for this?
• Lines: 164-174 is more suitable to be placed in the method section.
• Please provide a brief recommendation
• There are still many typo errors. Please correct them, i.e., Cu2O, ZrO2, use of abbreviations, …

Author Response

In response to the comments made by on the paper titled “Kinetic Behavior of Fabricated CuO/ZrO₂ Oxygen Carriers for Chemical Looping Oxygen Uncoupling” the following replies are made:

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,

lines 57ff. you cite some experimentally found activation energys for CuO coupled to some ceramic oxides. Assuming a Arrhenius model it would be interesting to know the second fitting parameter, the kinetic constant.

3.1, lines 110ff. you have a quite short description of the figures. Starting with fig. 1 I'd lke to read some quantitative evaluation. There is an aging with the first cycle and though ther seem to be some periodic change in reactivity there also seem to be a slight aging over the cycles.
With fig 2 from the figure it is hard to tell if there are specific changes in the peaks. I would assume a decrease in the second (the biggest) peak and perhaps a maximum at 3 cycles for the fifth peak, but I would prefer it, if you could present a quantitative evaluation.
Fig. 3 is nice, but as there are of course different particles some measures would be of interest, like changes in pore width and sizes of single structures. At 3 cycles I would assume there is some deposition but it seems to be less after 50 cycles, so I'd like you to tell me, what to see.

I am not fully satisfied with the explanation to fig. 5 showing a higher oxygen uncoupling rate for smaller particles. Transport phenomena as decribed are one possible explanation but a higher surface area with a greater number of active and reactive sites would be another. In respect to transport phenomena I would expect a higher diffusion resistance in the bulk for smaller particles and a higher diffusion resistance in the particle with greater particles. I miss an Arrhenius plots to indicate that experiments were conducted in the cinetically controlled regime. But the discussion of bulk and intra-particle effects might be matter of further research.

The experimental work is very extensive and thoroughly described.

I might have overread it, but I miss the reaction order of the recuction. As stated in eq. 5 and 6 you assume different reaction orders for oxidation and reduction but only stated that of the oxidation to 0.5.

It might be on purpose that you dont give the pre-exponetial factors, and there might be no pre-exponetial factors given in the cited literature, but if they were. Comparing those would be interesting, as determinig activation energy is not indipendant of determining the pre-exponetial factor.

All in all a very elaborated work.

Author Response

In response to the comments made by on the paper titled “Kinetic Behavior of Fabricated CuO/ZrO₂ Oxygen Carriers for Chemical Looping Oxygen Uncoupling” the following replies are made:

Please see the attachment.

Author Response File: Author Response.docx