Electrochemical Response of Highly Porous Percolative CGO Electrospun Membranes

Round 1

Reviewer 1 Report

The presented work is interesting and it is well organised and concise. However some points of the paper must be improved befor publication:

1.- In the experimental method, when the formulation of the ink is discussed, the authors use "Typical procedure", please provide references to show that is a commonly used procedure in the field.

2.-The effect of the temperature on the cristallites and grain size of the material and this is conlude by the debye scherre analysis of the XRD. However on the figure 1 the XRD is not very detailed. Please provide a zoom of the main folowed peaks to emphasise the change on the peaks related with the conclusions of the study. The changes are clear, but a zoom could help for further analysis.

3.-In order to discuss the shapes of the obtained Nyquist plots, as the author is doing in the manuscript " semi arcs can be distinguished in the plot..." the Nyquist have to be ploted on a square equidistanced set of axis. The distance for unit of Ohm has to be the same for x and y.

4.- In order to better discuss the Nyquist results I suggest to fit the plots with a simple RC equivalent circuit R+(RQ)+(RQ). This will allow to the authors to quantify the contributions and add a plot with to correlate the different (3) contributions (and related frequencies) to the calcination temperature o directly to the obtained sizes of the cristallites,  giving a much more accuracy to the discussion and quantifing the disscussed correlation.

5.-The conclusions should be improved with more detailed results. The fitting of the Nyquist plots will help on that.

 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript deals with a topic which is appropriate for Catalysts. In general, it is written clearly, with a correct English and it is well structured. The quality of the Figures is also high and the list of references sufficiently abundant and updated. It deserves an opportunity for publication but after many different corrections as follows:

Major comments

1) Nowadays the world of scientific publication is very competitive. Therefore, it is mandatory that the novelty of any new work is clearly explained by the authors. In this sense, in this particular case the authors themselves declared both in the introduction and in the discussion that a crystallites/grain size effect on the strength and and also on the conductivity of nanofibers had been previously reported. So, what is new here? How this manuscript contributes to the state-of-art? Is it the use of electrochemical impedance method or anything else? Please, make this more explicit, at least at the end of the introduction section so the reader has not to make the effort to go to literature and compare.

2) An scheme of the experimental set up for the materials preparation would be really appreciated for readers who are not familiar with the electrospinning process.

3) The TGA results should be shown because as the authors themselves say they are an important tool to understand how the fibers behave during the calcination process and, what is more important, to choose a set of meaningful temperatures for the calcination. If the problem is the extension of the manuscript the profiles could be provided in a Supplemmentary Materials Section. If the problem is that these results were already published, the authors should indicate the reference where they can be found.

4) It is at least surprising that the authors did not use N₂ physisorption taking into account that porosity is a key property of their materials and that this technique is so far present in almost any catalysis laboratory or if not relatively accesible. On the contrary the authors employed a much less conventional way to evaluate the pore volume. The authors should make this complementary mesurements or at least justify their absence.

5) Honestly, it is hard to estimate the dimensions of the grains by just looking at the provided SEM images. Perhaps, it can be done in the case of Figure 2e but it seems much more difficult for Figures 2 a-d. Any comment?

6) Why the EIS measurements were specifically conducted at 380, 480, 580 and 680 ºC? The authors should justify this selection.

7) The authors should carry out some chemical analysis (at least by one technique) to prove the presence of gadolinium and its relative content repect to cerium. Does the composition of the prepared materials match the nominal one?

Minor comments

1) Although English is in general correct, there are several corrections to be performed. I give some examples but please revise the whole text with care to avoid any other typo:

• Introduction, page 1, lines 10-11: either...or
• Introduction, page 2, line 22: increases
• Section 2.3, page 3, first line: for a few seconds
• Section 2.3, page 3, antepenultimate line: the covered frequency ranged from...
• Section 2.3, page 4, line 1: 20 % of oxygen in argon (or O₂(20%)/Ar)
• Section 2.3, page 4, after formulae: nanofibers, respectively;
• Page 6, line 22 after table: possible to estimate
• Figure 4b caption: must be reformulated.
• Page 12, line 4: compared

2) The way of expressing the units must be uniform. For example, sometimes the authors employ ºC/min while others ºC min^-1, and even K min^-1. Please separate these units from the number (not 20ºC, 26mm, etc), use h instead of hours and take care that the temperature symbol º is not underlined.

3) There is no need to include the Debye Scherrer equation. It is sufficiently known by the catalytic community.

4) The meaning of the EIS acronym must be inserted the first time it appears, not the second.

5) The first seventh lines of the Section 3 describe experimental details rather than results.

6) What is the point of proposing a samples nomenclature (CGO500, CGO600, etc) if it is not further used? See Figure 1a and Figure 2 caption.

7) Table 1 heading can be improved saying for example "Main properties determined by XRD^a and SEM^b". Now it just replicates the titles of the columns.

8) I suggest in general to write the labels in Figures 1-4 with minor letters like they are in their respective captions. Also, remove a, b, c and d in Figure 5 caption as the temperature is already indicated in each graph.

9) In Figure 3 caption HR-TEM and SAED must be exchanged.

10) What is the calcination temperature of the nanofibrous cell represented in Figure 4? (include it also in Page 8 mention). What is the small line at the left of the arrow in Figure 4b?

11) Reference numbers in the final list are duplicated (1. [1], 2. [2], ...)

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors improved the manuscript. So now it can be publishe in the present form.

 

Thanks

Reviewer 2 Report

The authors have answered properly all my questions/remarks and revised the manuscript accordingly. They created a new Supplementary Section which is a significant improvement. In my opinion it can be accepted for publication now, but please some minor typos must be first corrected:

1) In line 75 "prapration" should be "preparation"

2) In line 162 (and in the Supplementariy Information) Figure 3S should be Figure S3

3) Some ⁰C still appear with the ⁰ symbol underlined.