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Review of 'Active and Stable Platinum/Ionic Liquid/Carbon Nanotube Electrocatalysts for Oxidation of Methanol'

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Noteworthy results. An easy method for growth of Pt/IL/CNTs nano-hybrids
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    Rated 3 of 5.
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    Rated 3 of 5.
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    Rated 3 of 5.
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    Rated 3 of 5.
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    Rated 2 of 5.
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Active and Stable Platinum/Ionic Liquid/Carbon Nanotube Electrocatalysts for Oxidation of Methanol

(2014)
Platinum (Pt) nanoparticles (NPs) on carbon nanotubes (CNTs) from PtCl62– ions through a facile ionic liquid (IL)-assisted method has been developed and used for methanol oxidation. 1-Butyl-3-methylimidazolium (BMIM) with four different counter ions (PF6–, Cl–, Br–, and I–) have been tested for the preparation of Pt/IL/CNT nanohybrids, showing the counter ions of ILs play an important role in the formation of small sizes of Pt NPs. Only [BMIM][PF6] and [BMIM][Cl] allow reproducible preparation of Pt/IL/CNT nanohybrids. The electroactive surface areas of Pt/[BMIM][PF6]/CNT, Pt/[BMIM][Cl]/CNT, Pt/CNT, and commercial Pt/C electrodes are 62.8, 101.5, 78.3, and 87.4 m2 g-1, respectively. The Pt/[BMIM][Cl]/CNT nanohybrid-modified electrodes provide higher catalytic activity (251.0 A g–1) at a negative onset potential of -0.60 V than commercial Pt/C-modified ones do (133.5 A g–1) at -0.46 V. The Pt/[BMIM][Cl]/CNT electrode provides the highest ratio (4.52) of forward/reverse oxidation current peak, revealing a little accumulation of carbonaceous residues.
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    Review information

    10.14293/S2199-1006.1.SOR-CHEM.AYZQJS.v1.RCIHIO

    This work has been published open access under Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com.

    Review text

    This article must address the following issues.


  • In the introduction section, the authors must add more information on the properties of CNT as support for Pt in the improvement of DMFCs, indicating the absorption sites of Pt in pure CNT and adding more references in the discussion of the possible enhancement in density and quality of absorption sites.

  • The authors must insert more information on used Carbon Nanotubes (i.e., SW, MW, bundles, aggregated, isolated, diameter, purity, etc….)

  • In my experience, 5 minutes of sonication is not a very short sonication time for the solution of CNT bundles. The authors need to add more information on the choice of experimental parameters.

  • In the analysis of TEM images, the authors should add the histograms of particle size distribution and some information on particle density and distribution on CNT surface.

  • The presence of sp3 structure in pure carbon nanotube is not common, the authors must show the C1s of pure CNT before the growth of nano-hybrids, evaluate the grade of hybridization and explain the presence of carbon-like diamond states.

  • The authors should add a brief introduction in the supporting materials

  • Lastly, please consider consulting an English language editor for grammatical editing. The paper is difficult to read.

    Comments

    We would like to thank the referee’s for their valuable comments on our manuscript entitled “Active and stable platinum/ionic liquid/carbon nanotube electrocatalysts for oxidation of methanol (DOI: 10.14293/S2199-1006.1.SORCHEM.AYZQJS.v1). We have revised the manuscript according to the referee’s comments. 

    Reviewer 3 (Dr. Marianna Barberio)

    This article must address the following issues.

    1) In the introduction section, the authors must add more information on the properties of CNT as support for Pt in the improvement of DMFCs, indicating the absorption sites of Pt in pure CNT and adding more references in the discussion of the possible enhancement in density and quality of absorption sites.

    Response: More information on the properties of CNT as support for Pt in the improvement of DMFCs has been included [18-20]. Also we have included the discussion of the possible enhancement in density and quality of absorption sites. Pt NPs tend to get deposited on the defect sites and boundaries of the CNTs, which allows the as-deposited Pt NPs to be surrounded with more oxygen containing functional groups that favors the facile electron and proton transport during the MOR [18]. The inner and outer surfaces of CNTs and grooves at the junction of adjacent CNTs act as chemisorption sites for the Pt NPs [19]. The other factors that affected the distribution and deposition of Pt NPs on the surfaces of CNTs are interaction between the Pt ions and the functional groups, properties of CNTs and the functional group densities on the outer walls of CNTs [20].

    2) The authors must insert more information on used Carbon Nanotubes (i.e., SW, MW, bundles, aggregated, isolated, diameter, purity, etc….)

    Response: More information on used carbon nanotubes has been included. Multiwalled carbon nanotubes (MWCNTs, >90 % purity) as bundles with 10–30 nm in diameter were purchased from Seedchem Company Pty. Ltd. (Melbourne, Australia).

    3) In my experience, 5 minutes of sonication is not a very short sonication time for the solution of CNT bundles. The authors need to add more information on the choice of experimental parameters.

    Response: A stable dispersion was obtained when DMF solution (final volume of 10.0 mL) containing CNT (0.4 mg) and [BMIM][PF6] (400 μL, 4%) was sonicated for 5 min. We found that sonicating the mixture for longer time (>5min) did not increase the dispersing ability of CNTs. To avoid sonication-induced damage to the CNTs, 5 min sonication time was found to be optimal for our study. The sonication power and frequency were kept low and cold water with a surfactant was used in the sonicator bath to avoid heat-induced damage to the CNTs. This information has been included into the experimental section.

    3) In the analysis of TEM images, the authors should add the histograms of particle size distribution and some information on particle density and distribution on CNT surface.

    Response: We have included the histograms of particle size distribution to the TEM images. As displayed in the histogram provided in the inset of Fig. 1A, greater amount and better distribution (36 %) of Pt NPs with a diameter of 2.8 nm are formed on the CNT surface when using [BMIM][PF6]. Pt NPs with small size (2.6 nm) and greater distribution (38 %) are formed on the CNT surface when using [BMIM][PCl6] (inset to Fig. 1B).

    4) The presence of sp3 structure in pure carbon nanotube is not common, the authors must show the C1s of pure CNT before the growth of nano-hybrids, evaluate the grade of hybridization and explain the presence of carbon-like diamond states.

    Response: It can be evident from the literature that the characteristic peak at 285.3 eV is assigned to the sp3 hybridized carbon atoms and the surface defects of CNTs (Nature Photonics, 2014, 8, 239–24; Indian Journal of Engineering & materials Science, 2010, 17, 331-337). It has also been reported that CNT-nanodiamond material possess sp3 hybridized carbon atoms due to the sp3 carbon atoms of nanodiamond particles (Sci Rep. 2015, 5, 9379).  Commercially purchased CNTs were used without any purification and so it may have some surface defects. Several studies have also reported that the commercial CNTs prepared through chemical vapor deposition (CVD) process have some surface defects. The characteristic XRD peaks at 25.9°, 42.7°, and 54.2° correspond to the (002), (100), and (004) planes, respectively, of graphitized CNTs, in reference to JCPDS card No. 75-1621 however revealed the purity of CNTs.

    5) The authors should add a brief introduction in the supporting materials

    Response: More information on the properties of CNT as support for Pt in the improvement of DMFCs has been included [18-20]. Also we have included more discussion about the possible enhancement in density and quality of absorption sites to the introduction.

    6) Lastly, please consider consulting an English language editor for grammatical editing. The paper is difficult to read.

    Response: The manuscript has been carefully checked and the grammatical errors have been corrected.

    2015-09-15 08:12 UTC
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