Annealing and Plasma Effects on the Structural and Photocatalytic Properties of TiO₂ Fibers Produced by Electrospinning

Round 1

Reviewer 1 Report

This study is devoted to the thermal and H₂ plasma treatment of electrospinning TiO₂ fibers to improve their photocatalytic activity. It is well conducted. The photocatalysts with good potential are obtained and fully characterized. 

This article may be published after minor improvement.

Comments:

116 - "air pressure" change to "pressure"

119 - please, explain the treatment duration of namely 720 s

170 - interpretation of "straight and orderly" is needed. Probably such fiber alinement  is due to the surface charging of the fibers in plasma

190 - "from" change to "form"

211 - "it" change to "anatase"

258 - It is not good idea to write about IR-spectrum as an evidence method for the existence of O-vacancies

266 - after "increase" "of/in" is omitted

In figures 5-10 the samples are incorrectly denoted with "?"

In Fig. 6 XPS spectra of H₂ plasma-treated and untreated TiO2 fibers show elements change on the TiO₂ surface. After plasma treatment, the Ti³+ surface states are expected to appear. Normally Ti³⁺ - O_v pairs have to appear simultaneously just to preserve electroneutrality. See e.g. references

Kim, H. J., Kim, J., & Hong, B. (2013). Effect of hydrogen plasma treatment on nano-structured TiO2 films for the enhanced performance of dye-sensitized solar cell. Applied Surface Science, 274, 171–175. doi:10.1016/j.apsusc.2013.03.006

V. Madhavi, P. Kondaiah, Monalisa Ghosh, G. Mohan Rao, Hydrogen plasma-treated 1D/3D TiO2 nanorod array photoanode for efficient photoelectrochemical water splitting, Ceramics International, Volume 46, Issue 11, Part A, 2020, Pages 17791-17799, 10.14233/ajchem.2014.16031

However the authors do not observe the states of Ti³⁺ in the XPS spectra presented. Is this a consequence of the low resolution and sensitivity of the apparatus used? This point should be clarified.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Manuscript ID: catalysts-2013897

Title: Annealing and plasma effects on the structural and photocatalytic properties of TiO2 fibers produced by electrospinning

1/ The paper contains some grammatical errors and typo mistakes that should be corrected.

2/ The Abstract part should be more concise. It is too long. The abstract should clearly inform the important findings of the present study as well as some qualitative and quantitative results should be provided.

3/ The introduction part can be further improved. The authors are suggested to include recent references in the introduction part about previous studies performed on TiO2 nanomaterials.

4/ Also, there are many studies in the literature about TiO2 fibers, and their structural, morphological, physical and photocatalytic properties are widely discussed. Important studies should be reported in the Introduction part, and a comparison of the current study with the previously published one could be performed in the results and discussion part.

5/ Check symbols in different figures like the x-axis of Figure 5(a), symbols in XPS and FT-IR figures, etc...

6/ The structural properties should be further discussed and improved. Some other important structural parameters should be determined and discussed like lattice parameters, crystallite size, etc. The plausible reasons for their variations should be provided accordingly.

7/ Along with the presented SEM images, the authors should provide an analysis of grain size/diameter distribution.

8/ The authors should add the EDX spectra and atomic percentages of different samples.

9/ Surface area is a very important parameter in the present case. Therefore, I suggest that the BET surface area measurement should be added if possible.

10/ In FT-IR spectra, there are additional vibration bonds that are not described. I think that it would be better to report all vibrational bonds and their positions in a table.

11/ What does mean “taus diagram”? Do the authors mean “Tauc Plots”? It should be rechecked. The authors should provide some details on the determination of Eg values (not only giving references). Pls, provide an enlarged view of the Tauc plots (2.7 to 4 eV as maximum) to better determine the values of Eg. The discussion should be revised accordingly (there is a slight variation in Eg values).

12/ Before the presentation of the photocatalytic degradation rate and kinetics of photocatalytic degradation, the graphs of absorbance vs wavenumbers at different durations should be presented.

13/ Compare the photocatalytic results of the current samples with those for TiO2 (nano/micro)-fibers as well as other shaped nanomaterials.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The revised manuscript has been greatly improved. I think that it can be now accepted for publication.