Release of N<sub>2</sub> from the Carbon Nanotubes via High-Temperature Annealing

Choi, Hyun Chul; Bae, Seung Yong; Jang, Woo‐Sung; Park, Jeunghee; Song, H. J.; Shin, Hyun‐Joon; Jung, Hyunsung; Ahn, Jae-Pyoung

doi:10.1021/jp046098b

Cited by 97 publications

(59 citation statements)

References 39 publications

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“…[37][38][39] Oxidized nitrogen is oxidized pyridinic nitrogen, which is bonded to two carbon atoms and one oxygen atom ( ). [41][42][43][44] Molecular N 2 are nitrogen molecules adsorbed/intercalated at the carbon walls or trapped in the compartments, which has been confirmed by the X-ray absorption near-edge structure analysis 45 and scanning transmission X-ray microscopy. 46 From the peak areas, the doped nitrogen atoms are mainly pyridinic, graphitic, and oxidized nitrogen.…”

Section: Resultsmentioning

confidence: 76%

Nitrogen Doping Effects on Carbon Nanotubes and the Origin of the Enhanced Electrocatalytic Activity of Supported Pt for Proton-Exchange Membrane Fuel Cells

et al. 2011

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Carbon nanotubes (CNTs) and nitrogen-doped carbon nanotubes (CNx) were synthesized by the floating catalyst chemical vapor deposition (FCCVD) method. Pt nanoparticles were deposited onto the two catalyst supports with the ethylene glycol reduction method. Different from CNTs that contain straight hollow tubes, CNx contain a bamboolike structure with kinks along the tubes and more surface defects. X-ray photoelectron spectroscopy (XPS) confirms the nitrogen atoms in the graphite matrix and reveals the chemical natures of the doped nitrogen atoms. Carbon K-edge near-edge X-ray absorption fine structure (NEXAFS) and Raman characterizations reveal higher defectiveness in CNx than CNTs. The unique structure and surface property of CNx leads to a better dispersion of Pt nanoparticles on CNx than on CNTs, as revealed by TEM images. Pt supported on CNx (Pt/CNx) exhibited a higher electrochemical surface area (ECSA) and higher catalytic activity toward oxygen reduction reaction (ORR), in comparison to Pt supported on CNTs (Pt/CNTs). Better performance of Pt/CNx than Pt/CNTs has been confirmed by single-cell fuel cell tests.

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Section: Resultsmentioning

confidence: 76%

Nitrogen Doping Effects on Carbon Nanotubes and the Origin of the Enhanced Electrocatalytic Activity of Supported Pt for Proton-Exchange Membrane Fuel Cells

et al. 2011

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“…[12,13] All samples were baked at 400°C in ultra high vacuum (< 5×10 −9 mbar) in order to remove any atmospheric adsorbates before they were transferred to the experimental station. [14] The spectra were then recorded at ambient room temperature. …”

Section: Resultsmentioning

confidence: 99%

One-dimensional N2 gas inside single-walled carbon nanotubes

Kramberger

Thurakitseree

Koh

et al. 2013

Carbon

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The unexpected presence of a linear arrangement of co-axially oriented N 2 molecules inside aligned single-walled carbon nanotubes is revealed by high resolution near-edge x-ray absorption spectroscopy. The encapsulated N 2 molecules exhibit free stretching vibrations with a long electronic lifetime of the x-ray-excited anti-bonding π ⋆ states. Molecular dynamics simulations confirm that narrow-diameter nanotubes (d < 1 nm) are crucial for stabilizing the linear arrangement of aligned N 2 molecules.

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“…The N1s spectrum for PPy/rGO, CN x /G-600 and CN x /G-800 can be fitted to individual component peaks that represent pyrrolic N at a binding energy (Eb) of 399.8 eV, pyridinic N at a Eb of 398.3 eV and graphitic N at a Eb between 400.9-401.1 eV [26,27,31]. Additionally, the N1s spectra of the carbonized sample ( Figure 4(c) and (d)) also contain two other peaks at Ebs of 403.2 and 405.0 eV, corresponding to N-oxide and intercalated N 2 , respectively [39]. The total N content obtained from XPS as well as the pyrrolic, pyridinic and graphitic nitrogen content from the relative peak intensities depends on the annealing temperature, as plotted in Figure 4(e).…”

Section: Resultsmentioning

confidence: 99%

Carbon-nitrogen/graphene composite as metal-free electrocatalyst for the oxygen reduction reaction

Zhang

et al. 2011

Chin. Sci. Bull.

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Sheet-like carbon-nitrogen (CN x )/graphene composites with a high content of nitrogen (x  0.15) was prepared by the carbonization of polypyrrole (PPy)/reduced-graphene-oxide (rGO) composite at 600-800°C. We used rGO instead of graphene oxide (GO) sheets as a template and a substrate to immobilize PPy since the PPy/GO composite agglomerates easily because of the dehydration of excess oxygen-containing groups on the GO sheets during the drying process. The dried PPy/rGO intermediate and its derived CN x /graphene products retain their high dispersion and loose-powder features. The as-prepared CN x /graphene composites have a total nitrogen content of about 10 at% and their nitrogen state is mainly of pyridinic and graphitic type. CN x /graphene composites exhibit excellent performance for the oxygen reduction reaction (ORR) in terms of electrocatalytic activity, stability and immunity towards methanol crossover and CO poisoning, suggesting their potential as metal-free electrocatalysts for the ORR. Low temperature fuel cells are a high-efficiency and environment-friendly energy supply for future transport and portable applications [1,2]. However, despite the great efforts worldwide over the past few decades their wide application in daily life is still a challenge because of the scare resources, high cost and durability issues for the current commercial Pt/C catalysts, especially for cathodes where the oxygen reduction reaction (ORR) is kinetically slow [3][4][5]. Therefore, research into non-precious metals or even metal-free catalysts with high ORR activity and durability is absolutely crucial for the development of fuel cells. Currently, it is widely accepted that nitrogen-containing carbon including macrocycle molecules [6][7][8], polymers [4,9] and nanomaterials [10][11][12][13][14][15][16][17][18][19] are a type of important building block for the preparation of Pt-substituted catalysts.Iron-or cobalt-doped carbon-nitrogen (CN x ) compounds have comparable activity to Pt/C catalysts in acidic systems [4,7,9,20]. Polypyrrole modified carbon-supported cobalt hydroxide can act as cathode and anode catalysts in direct borohydride fuel cells [21,22]. Recent promising results involving metal-free PEDOT [5] and nitrogen-doped carbon nanotubes (NCNTs) [14][15][16][17][18][19] have been reported for alkaline systems giving excellent electrocatalytic activity, stability and immunity towards methanol crossover and CO poisoning. Particularly, NCNTs have attracted extensive interest because of their large surface area, good thermal and chemical stability as well as high electrical conductivity [14][15][16][17][18][19]. It has been revealed that increasing the nitrogen content and the number of defects in NCNT enhances its electrocatalytic activity toward the ORR [11,16]. In addition to one-dimensional CNTs, the emergence of graphene has opened up a new field in terms of research into two-dimensional (2D)

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Release of N₂ from the Carbon Nanotubes via High-Temperature Annealing

Cited by 97 publications

References 39 publications

Nitrogen Doping Effects on Carbon Nanotubes and the Origin of the Enhanced Electrocatalytic Activity of Supported Pt for Proton-Exchange Membrane Fuel Cells

Nitrogen Doping Effects on Carbon Nanotubes and the Origin of the Enhanced Electrocatalytic Activity of Supported Pt for Proton-Exchange Membrane Fuel Cells

One-dimensional N2 gas inside single-walled carbon nanotubes

Carbon-nitrogen/graphene composite as metal-free electrocatalyst for the oxygen reduction reaction

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Release of N2 from the Carbon Nanotubes via High-Temperature Annealing

Cited by 97 publications

References 39 publications

Nitrogen Doping Effects on Carbon Nanotubes and the Origin of the Enhanced Electrocatalytic Activity of Supported Pt for Proton-Exchange Membrane Fuel Cells

Nitrogen Doping Effects on Carbon Nanotubes and the Origin of the Enhanced Electrocatalytic Activity of Supported Pt for Proton-Exchange Membrane Fuel Cells

One-dimensional N2 gas inside single-walled carbon nanotubes

Carbon-nitrogen/graphene composite as metal-free electrocatalyst for the oxygen reduction reaction

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Product

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Release of N₂ from the Carbon Nanotubes via High-Temperature Annealing