An Accurate Growth Mechanism and Photocatalytic Degradation Rhodamine B of Crystalline Nb2O5 Nanotube Arrays
Round 1
Reviewer 1 Report
The manuscript entitled “An Accurate Growth Mechanism and Photocatalytic Degradation Rhodamine B of Crystalline Nb2O5 Nanotube Arrays” describes a new mechanism for the production of Nb2O5 photocatalytic nanotubes. In addition, the Authors tested the obtained photocatalysts with experimental runs aimed at the degradation of Rhodamine B. Before the acceptance for pubblication the following changes have to be carried out.
- Abstract: “Starting from the initial oxidation process, the “multi-point” corrosion of fluoride ions plays the key factor in the formation of nanotube arrays”. Please, describe the origin (NH4F) of fluoride ions and their role.
- Lines 27-28: “The introduction should briefly place the study in a broad context and highlight why it is important.” Please, remove this sentence.
- I suggest the removal of bombastic words, such as “tremendously”.
- Line 70-71: please, rephrase this sentence.
- The materials and method section have to be moved before the result and discussion section.
- Line 279: conducted or performed? Please, choose the verb.
- Section 3.3: it is not clear if the photocatalytic tests were caried out with UV or visible radiation.
- The images reported in figure 3 are unclear: the droplet is not visible. In addition, how have the Authors evaluated the contact angle
- Which kind of equipment was used to evaluate the Nb5+ concentrations? (see figure 4b)
- Some experimental runs have to be carried out to validate the discussion: 1) Rhodamine B direct photolysis (without catalyst); 2) Rhodamine B adsorption tests (with the catalysts in dark condition). Only in this way it is possible to evaluate the photocatalytic activity of the Nb2O5 photocatalytic nanotubes.
- Figure 7a: please, correct the legend.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors present the electrochemical synthesis of self-aligned Nb2O5 nanotube arrays with the detailed description of their growth mechanism. Furthermore, the authors described the effect of changing process parameters including water content and the amount of F- ions on morphological and other properties of the arrays. Finally, they correlated the process parameters and the materials characteristics with the photocatalytic discoloration of RhB dye solution. The gathered results and conclusions are interesting and worth to be published but there are several major issues that should be resolved before the manuscript can be published.
1) First of all, the English must be significantly improved. The authors should seek for help of native speaker or professional proofreading services. There are even some sentences that make the correct understanding of the interpretation very difficult or impossible. Without this, the manuscript should be rejected.
2) The mechanism of the formation of nanotube arrays is quite detailed without any citations. Based on what data are the conclusions then made?
3) How the peaks in FTIR data were assigned? Again, there are no citations.
4) I have doubts about the interpretation of the FTIR data in Figure 4 (and 5). There is probably a small peak assigned to Nb-OH groups in all presented spectra that is more or less the same in all spectra. I agree that it seems that the peaks assigned to Nb oxides grow in intensity. But to reliably estimate its intensity, the spectra should be background corrected (to the same level) and these data should be presented.
5) SEM data in Figures 4 and Five are almost illegible - there is almost nothing to see. I suggest to use high-resolution SEM data with proper scale and put them in the supplementary data that the reader can see what is claimed by the authors.
6) How the contact angle was measured? There should be also an explanation why the contact angle is important and how is related to the formation of nanotubes.
7) UV-Vis spectra - there is a clear strong difference in shape of the spectra of the samples with water content compared to samples prepared only in glycol in the region 200-300 nm. What is the explanation for that?
8) What is precision and reliability of the photocatalytic test? Does it makes sense to present numbers with two digits after decimal point? The confidence intervals should be included with the measured data.
9) In the Figure 7a, there are two samples with the same description (S-0.35)
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
the manuscript has been sufficiently improved
Reviewer 2 Report
The Authors improved the manuscript sufficiently to be published.
