Article

Distribution and Structure of N Atoms in Multiwalled Carbon Nanotubes Using Variable-Energy X-Ray Photoelectron Spectroscopy

Department of Chemistry, Korea Advanced Institute of Science and Technology, Sŏul, Seoul, South Korea
The Journal of Physical Chemistry B (Impact Factor: 3.3). 04/2005; 109(10):4333-40. DOI: 10.1021/jp0453109
Source: PubMed

ABSTRACT

We investigated the inhomogeneous distribution of concentration and electronic structure of the nitrogen (N) atoms doped in the multiwalled carbon nanotubes (CNTs) by variable-energy X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure, and electron energy-loss spectroscopy. The vertically aligned N-doped CNTs on the substrates were grown via pyrolysis of iron phthalocyanine (FePc), cobalt phthalocyanine (CoPc), and nickel phthalocyanine (NiPc) in the temperature range 750-1000 degrees C. They usually have a bamboo-like structure, and the diameter is in the range of 15-80 nm. As the photon energy of XPS increases from 475 to 1265 eV, the N content increases up to 8 atomic %, indicating a higher N concentration at the inside of nanotubes. We identified three typed N structures: graphite-like, pyridine-like, and molecular N(2). The pyridine-like N structure becomes significant at the inner walls. Molecular N(2) would exist as intercalated forms in the vicinity of hollow inside. The XPS valence band analysis reveals that the pyridine-like N structure induces the metallic behaviors. The CNTs grown using NiPc contain the higher content of pyridine-like structure compared to those grown using FePc and CoPc, so they exhibit more metallic properties.

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    • "Two first-order Raman spectra of CN x P y synthesized with 50 mg of TPP and CN x were plotted in Fig. 6. The band located at $1342 cm À1 (D-band) is originated from atomic displacement and disorder induced features caused by lattice defect, distortion, or the finite particle size [31]. The band at $1568 to 1582 cm À1 (G-band) indicates the formation of well-graphitized CNTs [32]. "

    Full-text · Dataset · Jan 2015
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    • "Around 900°C, the nitrogen contents of the carbon layer decrease, and the crystallinity of the graphene layers increases due to the catalytic act of metallic Fe nanoparticles. It is well known that the graphitic carbon from the decomposition of metal-phthalocyanine typically contains approximately 1% to 8% of nitrogen contents [22,24]. Especially, Fe-Pc is known as an efficient carbon source for producing a highly graphitic carbon, where its Fe particles in the final product can be easily removed by simple acid leaching. "
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    ABSTRACT: The intrinsic low conductivity of sulfur which leads to a low performance at a high current rate is one of the most limiting factors for the commercialization of lithium-sulfur battery. Here, we present an easy and convenient method to synthesize a mono-dispersed hollow carbon sphere with a thin graphitic wall which can be utilized as a support with a good electrical conductivity for the preparation of sulfur/carbon nano-composite cathode. The hollow carbon sphere was prepared from the pyrolysis of the homogenous mixture of the mono-dispersed spherical silica and Fe-phthalocyanine powder in elevated temperature. The composite cathode was manufactured by infiltrating sulfur melt into the inner side of the graphitic wall. The electrochemical cycling shows a capacity of 425 mAh g ¿1 at 3 C current rate which is more than five times larger than that for the sulfur/carbon black nano-composite prepared by simple ball milling.
    Full-text · Article · Aug 2013 · Nanoscale Research Letters
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    • "Two first-order Raman spectra of CN x P y synthesized with 50 mg of TPP and CN x were plotted in Fig. 6. The band located at $1342 cm À1 (D-band) is originated from atomic displacement and disorder induced features caused by lattice defect, distortion, or the finite particle size [31]. The band at $1568 to 1582 cm À1 (G-band) indicates the formation of well-graphitized CNTs [32]. "
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    ABSTRACT: Phosphorus–nitrogen doped multiwalled carbon nanotubes (CNxPy) were prepared using a floating catalyst chemical vapor deposition method. Triphenylphosphine (TPP), as phosphorus (P) precursor, was used to control the structure of the CNxPy. Transmission electron microscope (TEM) observation indicated that with the increase of TPP amount, the outer diameter and wall thickness of the CNxPy gradually increased, while their inner diameter decreased. TEM and backscattered electron imaging revealed that structural changes of the nanotubes could be attributed to the shape change of the catalyst particles, from conical for nitrogen-doped carbon nanotubes (CNx) to elongated for CNxPy, with the addition of TPP. X-ray photoelectron spectroscopy analysis demonstrated that the P content in CNxPy can reach as high as 1.9 at.%. Raman analysis indicated that CNxPy had a lower crystallinity than CNx.
    Full-text · Article · Dec 2011 · Carbon
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