Morphological Evolution of La₂NiO₄ Coatings Synthesized by Reactive Magnetron Sputtering (RMS) at High Pressure as Cathode for Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors prepared the coatings of La2NiO4 (LNO) with a K2NiF4 structure via the reactive magnetron sputtering (RMS) and subsequent annealing processes, characterized their partial physicochemical properties, and investigated their evolution of the structures and morphologies. This work contains some new results and could be considered for publication. However, the authors should revise their manuscript before acceptance for publication according to the following comments:

1.        What are the contents of LNO, YSZ, and LNO in the LNO/YSZ/LNO symmetrical half-cell?

2.        What is the effect of a small amount of La3Ni2O7 on the performance of the La2NiO4 coatings?

3.        How about the effects of crystal sizes and pore sizes on the performance of the La2NiO4 coatings?

4.        What are the roles of LNO, YSZ, and LNO in enhancing the electrochemical performance?

5.        A comparison on the performance of the as-obtained typical sample should be made with those of the related samples reported in the literature.

6.        There are some inappropriate English words or expressions in the manuscript. The authors should carefully polish the English of the whole manuscript.

Comments on the Quality of English Language

There are some inappropriate English words or expressions in the manuscript. The authors should carefully polish the English of the whole manuscript.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I have reviewed the article entitled “Morphological Evolution of La2NiO4 Coatings Synthesized by Reactive Magnetron Sputtering (RMS) at High Pressure as IT- SOFC Cathode” by Briois et al submitted to Coatings / MDPI. Reactive magnetron sputtering technique employed by the authors in the submitted work allows the deposition of thin and dense layers, which are able to be used as electrolyte or diffusion barrier layers in fuel cells. Authors have explored the feasibility of producing a thin La2NiO4 coatings having porous morphology exhibits lower polarization resistance and activation energy. The area of research is significant and addresses the application of magnetron sputtering in SOFCs cathode preparation. The manuscript itself is written OK but the main concern of this paper and the areas that require clarification are given below.

·         Please provide the reference cathode materials that are currently used in SOFC.

·         Can the oxide coatings occur at high sputtering rates?

·         What is IT SOFC? IT stands for.

·         Will the dense cathode layer result in low electrochemical performance as demonstrated in literature?

·         As the authors have already demonstrated this Ln2NiO4 coatings on half/single cells, then what is the originality of the current work, please revise this in the last paragraph of the introduction section.

·         various surface modification techniques have been employed to improve the performance of SOFC cathodes, please include this in the appropriate section using the literature doi.org/10.1021/acs.energyfuels.0c02920.

·         If the annealing temperature is increased over 1100 degrees C what would be the consequence in Figure 3 XRD pattern?

·         In Figure 5 will the thickness be proportionally increased at 12oo degree C?

·         Page 8, line 223, where is the needle-like shape morphology, please provide the evidence in the SEM images.

·         Figure 8, subsequently annealed for 120 h? Is it common to heat for such a long time?

·         Page 16, lines 260 -264, the background of Nyquist plots must be referred back to the literature such as 10.1039/C8NR03824D; and doi.org/10.1002/cplu.201600294

·         Please provide the values for the constants CPE, Rs, and other variables used in Figure 10.

·         Section 4, in the conclusion it is stated that “other morphologies in this work” Have the other morphologies stated in this work?

·         What is the overall impact of annealing at different times that the authors have observed, this must be emphasized in the conclusion section.

·         Has any cell tests (voltammetry) been performed?

 

 

 

Comments on the Quality of English Language

Some edits in the language are required.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have basically modified their manuscript according to the Reviewers' comments. It may be now acceptable for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed my queries raised earlier (in round 1) satisfactorily. In this reviewer's opinion, this version should be suitable for publication.