Adsorption Kinetics of NO2 Gas on Pt/Cr-TiO2/Pt-Based Sensors
, Qawareer Fatima 1, Ahmar Mehmood 1, Asim Shahzad 1, Yinwen Ji 1,2 and Bilge Saruhan 4Round 1
Reviewer 1 Report
The article "Adsorption kinetics of NO2 gas on Pt/Cr-TiO2/Pt based sensors" is devoted to obtaining new gas sensors and contains interesting information. The work can be published in «Chemosensors» after significant changes:
1) The authors pay a lot of attention to NO2 in the introduction, in this case it is necessary to indicate its TLV and compare these values ​​with the data obtained experimentally.
2) When analyzing XRD data, the authors cite 3 PDF-cards, 2 of which refer to anatase and rutile. Which phase does the PDF 73-1570 card belong to?
3) Is there a shift in the main reflections of TiO2 in the above X-ray diffraction patterns. If so, then this should be discussed in the text of the article. In the article, the authors argue that the temple is embedded in a TiO2 lattice (Equation 11), although there is no direct evidence for this. If this is the case, then upon doping with Cr, the main reflections should shift.
4) In some figures and equations (Fig. 3, 5, etc.), the design of some elements is unsuccessful. The micrographs do not show risks and signatures on a gray background, in Fig. 5, the values ​​along the axes are poorly distinguishable. In fig. 5 it is necessary to indicate "°C" for temperatures. In equation (10), the indices are difficult to distinguish. I suggest that the authors correct this and once again check all the data presented for an adequate perception by the reader.
5) In my opinion, fig. 3 (j) is very informative, I suggest the authors make it separately for better perception.
6) I suggest the authors better understand the mechanism of the reaction of NO2 with TiO2 and give the reaction equation referring to the literature data (similar to equation 11).
7) Perhaps the following article will be useful for citation in this work: DOI: 10.1007/s10971-019-04979-4.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This manuscript has demonstrated a MOS NO2 sensor based on Cr-doped TiO2 with the adsorption kinetics investigations. The microstructure and materials components are well characterized, as well as the sensing performance. However, the main topic of this manuscript is not clear and in-depth, and the manuscript needs some major revisions before it can be accepted by “Chemosensors”.
My detailed comments are as below:
- Some text errors. Line 238, should not be Fig. 4(a); Line 340, no Fig. 7(d) can be found; Line 378, “While as per our XRD analysis”.
- Since the title give the main concerned topic of this manuscript: adsorption kinetics, the XRD, SEM and GDOES analysis can be shortened, which is too long in the present version and distract readers.
- Line 232-233, authors indicate that undoped TiO2 shows n-type NO2 response character, please give corresponding results.
- Line 241-242, “a significant drift in baseline resistance” lacks of experimental data.
- Fig 5(c), It can be seen that NO2 with a concentration of 50, 75, 125ppm generate nearly the same response, how do authors view that? This might have some influence on the latter kinetic data fitting.
- Line 275, why do authors estimate the response value since the real response value can be measured? The estimate value is undoubtedly not so convincing as the real value.
- The positions of Figures 6 and 7 may be reversed, please carefully check.
- Line 376, it was stated that 2 at.% of Cr dopant yields p-type sensor behavior, please give experiment data.
- Line 379-380, the statement about band gap difference lacks of experimental data.
- The kinetic investigation only considered the behavior of NO2. In fact, in MOS sensing, oxygen adsorption is also important which might be considered in the kinetic model.
- The present kinetic model investigation is not in-depth enough, authors only give the fitting results comparisons of different models and choose a best fitting model. The discussion about the interaction mode behind these models are lacking.
- It is better to give a simple schematic illustration of the sensing mechanism.
- What is the purpose of Cr doping since the adsorption kinetics is the main topic in this manuscript? Because pure TiO2 can also perform the NO2 sensing tests. Besides, the NO2 sensing performance of Cr-doped TiO2 is not so remarkable, as recent NO2 sensing studies have already realized room-temperature ppb-level sensing.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I agree with the authors' answers
Reviewer 2 Report
The authors have made revisions as reviewers suggest, and the manuscript can be accepted now.
Author Response
Thank you for your comments.
