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Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free eletrocatalysts for oxygen reduction reaction.

Jeon IY, Choi HJ, Choi M, Seo JM, Jung SM, Kim MJ, Zhang S, Zhang L, Xia Z, Dai L, Park N, Baek JB - Sci Rep (2013)

Bottom Line: A series of edge-selectively halogenated (X = Cl, Br, I) graphene nanoplatelets (XGnPs = ClGnP, BrGnP, IGnP) were prepared simply by ball-milling graphite in the presence of Cl2, Br2 and I2, respectively.The newly-developed XGnPs can be well dispersed in various solvents, and hence are solution processable.First-principle density-functional calculations revealed that halogenated graphene edges could provide decent adsorption sites for oxygen molecules, in a good agreement with the experimental observations.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary School of Green Energy, Low-Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon, Ulsan, South Korea.

ABSTRACT
A series of edge-selectively halogenated (X = Cl, Br, I) graphene nanoplatelets (XGnPs = ClGnP, BrGnP, IGnP) were prepared simply by ball-milling graphite in the presence of Cl2, Br2 and I2, respectively. High BET surface areas of 471, 579 and 662 m(2)/g were observed for ClGnP, BrGnP and IGnP, respectively, indicating a significant extent of delamination during the ball-milling and subsequent workup processes. The newly-developed XGnPs can be well dispersed in various solvents, and hence are solution processable. Furthermore, XGnPs showed remarkable electrocatalytic activities toward oxygen reduction reaction (ORR) with a high selectivity, good tolerance to methanol crossover/CO poisoning effects, and excellent long-term cycle stability. First-principle density-functional calculations revealed that halogenated graphene edges could provide decent adsorption sites for oxygen molecules, in a good agreement with the experimental observations.

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SEM images.(a) the pristine graphite with average grain size :150 μm. The average grain sizes of XGnPs reduced to less than 1 μm: (b) ClGnP; (c) BrGnP; (d) IGnP. Scale bars are 1 μm. (e) EDX spectra. (f) XRD diffraction patterns. Inset is magnified XRD diffraction patterns from the pink rectangle. The relative [002] peak intensities of XGnPs are less than 0.4% of that of the pristine graphite, indicating that the great extent of graphite has been deliminated into edge-halogenated graphene nanoplatelets (XGnPs). (g) A schematic representation for the edge expansions of XGnPs caused by the edge-halogens.
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f2: SEM images.(a) the pristine graphite with average grain size :150 μm. The average grain sizes of XGnPs reduced to less than 1 μm: (b) ClGnP; (c) BrGnP; (d) IGnP. Scale bars are 1 μm. (e) EDX spectra. (f) XRD diffraction patterns. Inset is magnified XRD diffraction patterns from the pink rectangle. The relative [002] peak intensities of XGnPs are less than 0.4% of that of the pristine graphite, indicating that the great extent of graphite has been deliminated into edge-halogenated graphene nanoplatelets (XGnPs). (g) A schematic representation for the edge expansions of XGnPs caused by the edge-halogens.

Mentions: Scanning electron microscopy (SEM) images show an obvious size reduction from a large grain size of :150 μm for the pristine graphite (Figure 2a) to a much smaller grain size of <1 μm for XGnPs (Figures 2b–2d) by ball-milling. The size reduction implies C-C bond breakings in the graphitic structures, and thus in-situ generation of active carbon species to react with halogens. The presence of Cl, Br and I in the resultant XGnPs are clearly evident by energy dispersive X-ray (EDX) spectroscopic (Figure 2e) measurements with element mapping (Figure S2 and Table S2) and elemental analyses (EA) (Table S1).


Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free eletrocatalysts for oxygen reduction reaction.

Jeon IY, Choi HJ, Choi M, Seo JM, Jung SM, Kim MJ, Zhang S, Zhang L, Xia Z, Dai L, Park N, Baek JB - Sci Rep (2013)

SEM images.(a) the pristine graphite with average grain size :150 μm. The average grain sizes of XGnPs reduced to less than 1 μm: (b) ClGnP; (c) BrGnP; (d) IGnP. Scale bars are 1 μm. (e) EDX spectra. (f) XRD diffraction patterns. Inset is magnified XRD diffraction patterns from the pink rectangle. The relative [002] peak intensities of XGnPs are less than 0.4% of that of the pristine graphite, indicating that the great extent of graphite has been deliminated into edge-halogenated graphene nanoplatelets (XGnPs). (g) A schematic representation for the edge expansions of XGnPs caused by the edge-halogens.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672906&req=5

f2: SEM images.(a) the pristine graphite with average grain size :150 μm. The average grain sizes of XGnPs reduced to less than 1 μm: (b) ClGnP; (c) BrGnP; (d) IGnP. Scale bars are 1 μm. (e) EDX spectra. (f) XRD diffraction patterns. Inset is magnified XRD diffraction patterns from the pink rectangle. The relative [002] peak intensities of XGnPs are less than 0.4% of that of the pristine graphite, indicating that the great extent of graphite has been deliminated into edge-halogenated graphene nanoplatelets (XGnPs). (g) A schematic representation for the edge expansions of XGnPs caused by the edge-halogens.
Mentions: Scanning electron microscopy (SEM) images show an obvious size reduction from a large grain size of :150 μm for the pristine graphite (Figure 2a) to a much smaller grain size of <1 μm for XGnPs (Figures 2b–2d) by ball-milling. The size reduction implies C-C bond breakings in the graphitic structures, and thus in-situ generation of active carbon species to react with halogens. The presence of Cl, Br and I in the resultant XGnPs are clearly evident by energy dispersive X-ray (EDX) spectroscopic (Figure 2e) measurements with element mapping (Figure S2 and Table S2) and elemental analyses (EA) (Table S1).

Bottom Line: A series of edge-selectively halogenated (X = Cl, Br, I) graphene nanoplatelets (XGnPs = ClGnP, BrGnP, IGnP) were prepared simply by ball-milling graphite in the presence of Cl2, Br2 and I2, respectively.The newly-developed XGnPs can be well dispersed in various solvents, and hence are solution processable.First-principle density-functional calculations revealed that halogenated graphene edges could provide decent adsorption sites for oxygen molecules, in a good agreement with the experimental observations.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary School of Green Energy, Low-Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon, Ulsan, South Korea.

ABSTRACT
A series of edge-selectively halogenated (X = Cl, Br, I) graphene nanoplatelets (XGnPs = ClGnP, BrGnP, IGnP) were prepared simply by ball-milling graphite in the presence of Cl2, Br2 and I2, respectively. High BET surface areas of 471, 579 and 662 m(2)/g were observed for ClGnP, BrGnP and IGnP, respectively, indicating a significant extent of delamination during the ball-milling and subsequent workup processes. The newly-developed XGnPs can be well dispersed in various solvents, and hence are solution processable. Furthermore, XGnPs showed remarkable electrocatalytic activities toward oxygen reduction reaction (ORR) with a high selectivity, good tolerance to methanol crossover/CO poisoning effects, and excellent long-term cycle stability. First-principle density-functional calculations revealed that halogenated graphene edges could provide decent adsorption sites for oxygen molecules, in a good agreement with the experimental observations.

Show MeSH
Related in: MedlinePlus