Extreme Oxygen Sensitivity of Electronic Properties of Carbon Nanotubes

Collins, Philip G.; Bradley, Keith; Ishigami, Masa; Zettl, A.

doi:10.1126/science.287.5459.1801

Cited by 2,809 publications

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“…540 eV was also observed for both N-graphene and C-graphene, 29,30 possibly due to the incorporation physically adsorbed oxygen as in the case with CNTs. 28,31 Thus, the higher O 1s peak relative to the corresponding C 1s peak seen for the N-graphene than that of the C-graphene suggests a stronger O 2 adsorption on the former, an additional advantage as the ORR electrode. The absence of any Ni peak in the XPS spectrum for the N-graphene clearly indicates that the Ni catalyst residues, if any, have been completely removed by the HCl solution.…”

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confidence: 99%

Nitrogen-Doped Graphene as Efficient Metal-Free Electrocatalyst for Oxygen Reduction in Fuel Cells

et al. 2010

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. ¶ These authors contributed equally.P latinum (Pt) nanoparticles have long been regarded as the best catalyst for the oxygen reduction reaction (ORR) in fuel cells, though the Pt-based electrode still suffers from its susceptibility to timedependent drift and CO deactivation. 1Ϫ3 Furthermore, the high cost of the Pt catalysts, together with the limited reserves of Pt in nature, has been shown to be the major "showstopper" to mass market fuel cells for commercial applications. That is why the large-scale practical application of fuel cells has not been realized, though alkaline fuel cells with platinum as an ORR electrocatalyst were developed for the Apollo lunar mission in the 1960s. 4 Along with recent intensive research efforts in reducing or replacing Ptbased electrodes in fuel cells, 3,5Ϫ11 we have found that vertically aligned nitrogencontaining carbon nanotubes (VA-NCNTs) produced by pyrolysis of iron(II) phthalocyanine (a metal heterocyclic molecule containing nitrogen), 12 in either the presence or absence of additional NH 3 vapor, 3 could act as effective metal-free ORR electrocatalysts. The metal-free VA-NCNTs were shown to catalyze a four-electron ORR process free from CO "poisoning" with a 3-time higher electrocatalytic activity, smaller crossover effect, and better long-term operation stability than that of commercially available Pt-based electrodes (C2Ϫ20, 20% platinumonVulcanXC-72R; E-TEK) in alkaline electrolytes. 3 On the basis of the experimental observations and quantum mechanics calculations, we attributed the improved catalytic performance to the electronaccepting ability of the nitrogen atoms, which creates a net positive charge on adjacent carbon atoms in the nanotube carbon plane of VA-NCNTs to readily attract electrons from the anode for facilitating the ORR. 3 Uncovering this new ORR mechanism in nitrogen-doped carbon nanotube electrodes is significant as the same principle could be applied to the development of various other metal-free efficient ORR catalysts for fuel cell applications.The recent discovery of graphene has opened up a new era of 2-dimensional (2D) fundamental science and potential technology. 13Ϫ15 As mother of all graphitic forms, graphene is a building block for carbon materials of all other dimensionalities, such as 0D buckyballs, 1D nanotubes, and 3D graphite. Having many similarities to carbon nanotubes (CNTs) in structure and property, including its high aspect ratio (the ratio of lateral size to thickness), large surface, rich electronic states, and good mechanical properties, graphene is an attractive candidate for potential uses in many areas where the CNTs have been exploited. Superior to CNTs, the one atomic-thick graphene sheets with a 2D planar geometry will further facilitate electron transport, 16 and hence the more effective electrode materials.

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confidence: 99%

Nitrogen-Doped Graphene as Efficient Metal-Free Electrocatalyst for Oxygen Reduction in Fuel Cells

et al. 2010

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“…The relative contribution of each component is a function of network thickness: with VRH dominating the thinnest networks and metallic contribution increasing with thickness [16,17]. The use of enriched metallic SWNT populations and purification through ultracentrifugation inevitably result in good electrical performance of SWNT networks through minimising both the semiconductor-metal junction density and disorder [7]. The high inter-bundle contact resistance is the main obstacle to enhancement of the electrical performance of SWNT networks [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…Handling in air also results in significant modification of electrical conductivity through exposure to oxygen and atmospheric humidity [7,8] through donor-or acceptor-like charge transfer from weakly absorbed species which affects the position of the Fermi energy and hence the conductivity of the network. The absorption of gaseous species on the surface or inside of a nanotube bundle is stronger than that on an individual SWNT but is reversible [8,9].…”

Section: Introductionmentioning

confidence: 99%

High electrical conductance enhancement in Au-nanoparticle decorated sparse single-wall carbon nanotube networks

McAndrew

Baxendale

2013

Nanotechnology

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We report high electrical conductivity enhancement in sparse single-walled carbon nanotube networks by decoration with Au nanoparticles. The optimised hybrid network exhibited a sheet resistance of 650 /sq: 1/1500 of the resistance of the host undecorated network, with a negligible optical transmission penalty (>90% transmittance at 550 nm wavelength). The electrical transport at room temperature in host and decorated networks was dominated by 2-dimensional variable range hopping.The high conductance enhancement was due to positive charge transfer from the decorating Au nanoparticles in intimate contact with the host network causing a Fermi energy shift into the high density of states at a van Hove singularity and enhanced electron delocalisation relative to the host network which beneficially modifies the hopping parameters in such a way that the network behaves as an integral whole. The effect is most pronounced when the nanoparticle diameter is comparable to the electron mean free path in the bulk material at room temperature and there is minimum nanoparticle agglomeration. For higher than optimal values of nanoparticles per unit area or nanoparticle diameter, the conductivity enhancement is countered by metallic inclusions in the current pathways that are of higher resistance than the VRH-controlled elements.

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“…For example, R is reduced only by 0.265% at E = 0.08 mV/Å and by 0.355% at 0.10 mV/Å. Experiments however were carried out in ambient condition and F C may, to some extent, be compromised by intercalated O 2 molecules [15]. We have tested D 2 in vacuum at 300 K (a) and 77 K (b), and recorded data is compared with Figure 5(b) ((c), Table 3).…”

Section: Resultsmentioning

confidence: 99%

Use of Aligned Carbon Nanotubes as Electric Field Sensors

Lu¹,

Tsai²,

Wei³

et al. 2013

PIER

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Abstract-Application of electric field in normal to aligned carbon nanotubes creates Coulomb forces at intertube junctions and tubes become closely packed. Packed structure facilitates intertube transfer of carriers and reduced resistance is found to scale with field strength. Aggregated nanotubes are therefore used as field sensors and sensitivity is evident by drastic fluctuations of resistance. Sensing mechanism is discussed and verified.

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Extreme Oxygen Sensitivity of Electronic Properties of Carbon Nanotubes

Cited by 2,809 publications

References 20 publications

Nitrogen-Doped Graphene as Efficient Metal-Free Electrocatalyst for Oxygen Reduction in Fuel Cells

Nitrogen-Doped Graphene as Efficient Metal-Free Electrocatalyst for Oxygen Reduction in Fuel Cells

High electrical conductance enhancement in Au-nanoparticle decorated sparse single-wall carbon nanotube networks

Use of Aligned Carbon Nanotubes as Electric Field Sensors

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