Giving New Life to Waste Cigarette Butts: Transformation into Platinum Group Metal-Free Electrocatalysts for Oxygen Reduction Reaction in Acid, Neutral and Alkaline Environment

Round 1

Reviewer 1 Report

This paper reports the derivation of catalysts  from waste cigarette butts. The idea and results are quite interesting to readers. Before accepted for publication, the following parts should be improved.

1. What kind of waste cigarette butts did the authors used? It is best to provided the composition of the butts.

2. During the heattreating process, 450, 600, 750 or 900°C were selected? Why? Please give the reason for selecting the temperature.

3. The CV tests and long-time running stability tests should be provided in the paper.

4. The English should be smoothed.

Author Response

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Reviewer 2 Report

Review on

“Giving a new life to waste cigarette butts: transformation into platinum group metal-free electrocatalysts for oxygen reduction reaction in acid, neutral and alkaline environment”

 

Testa et al. report on an experimental study in which waste cigarette butts were chosen as starting material for the so called MNC catalysts. The effect of pyrolysis temperature in the range of 450 – 900 °C was compared in this study. FePc was chosen as Fe and N precursor to obtain FeNC catalysts based on the pyrolyzed cigarette butts. The authors report the catalytic ORR activity and selectivity in acid, base and neutral environment. The study is well structured and very detailed. Also, the authors referred to suitable literature in discussing the results. I would recommend publication after successful minor revision.

Please find my comments below:

·        Line 147: It should be four instead of three.

·      What influence does the FeNC pyrolysis temperature have on the physical properties of the catalysts? Especially in case of sample cig_450, where the treatment temperature was lower then the FeNC pyrolysis temperature?

·         Low resolution of Fig 1, please improve.

·         Add XRD pattern of cig_BM in Fig 2a. Why are there two (002) peaks?

·         Raman spectroscopy: Why didn’t the authors fit the spectra to extract more information on graphitic and amorphous character?

·         Lines 224/225: Please try to explain the correlations found by TEM and XRD in more detail. Furthermore, is there the occurrence of a carbon nanotube in Fig 3b)? And if so, what would this mean regarding the catalytic potential of the material?

·         Regarding the XPS fitting results: Please show raw data from Fig S4 in Fig 4.

·         Line 326: Are the S_BET values really outstanding in comparison to other FeNC catalysts? The authors should compare their results to literature, especially with respect to the overall low mesopore volume.

·         On the discussion of ORR selectivity: The mechanism can either proceed via a 4-electron pathway or a 2x2-electron pathway and the number of transferred electrons indicates what pathway is mostly prevailing. During the discussion of the results it seems that the authors refer to three different pathways.

·         Why didn’t the authors measure or at least compare to a (commercial) FeNC reference? Please check Primbs et al., Energy Environ. Sci., 2020, 13, 2480. This study covers different Fe-N-C catalysts. At least compare the values activity from this study to your own word and comment on differences.

·         More details in exp. Part. For example, how was the I_D/I_G ratio determined?

·         The authors used a Pt wire as counter electrode in their RRDE measurements. This can lead to interference of the “real” ORR activity and is therefore replaced by carbon-based CEs in current literature. The authors shroud comment and estimate the impact on the ORR activity in their study.

·         Lines 666/667: Please remove.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

In this manuscript, Testa et. al described the transformation of cigarette waste butts into platinum group metal-free electrocatalysts for oxygen reduction. The data were presented in an appropriate way, but there are some issues that I recommend the authors to consider after which the manuscript can be published. Detailed comments are as follows:

1) The English needs to be carefully polished, including text and caption
2) The introduction part should be rewritten. The authors should point out the advantages of their materials and technique more straightly by adding ref Microchimica Acta 186, 1-10, Polymers 14 (4), 845.
3) The author should revised the figure 3 with high quality.
4) The author should provide the SEM images and TGA results.
5) Please revise the conclusion based on the experiment and their results only not like introduction section.

Author Response

Response attached

Author Response File: Author Response.pdf