[Liu, Chang; Li, Feng; Ma, Lai-Peng; Cheng, Hui-Ming] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China.;Cheng, HM (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, 72 Wenhua Rd, Shenyang 110016, Peoples R China;cheng@imr.ac.cn

Advanced Materials for Energy Storage

Raman spectroscopy of carbon nanotubes

Spectrofluorimetric measurements on single-walled carbon nanotubes (SWNTs) isolated in aqueous surfactant suspensions have revealed distinct electronic absorption and emission transitions for more than 30 different semiconducting nanotube species. By combining these fluorimetric results with resonance Raman data, each optical transition has been mapped to a specific (n,m) nanotube structure. Optical spectroscopy can thereby be used to rapidly determine the detailed composition of bulk SWNT samples, providing distributions in both tube diameter and chiral angle. The measured transition frequencies differ substantially from simple theoretical predictions. These deviations may reflect combinations of trigonal warping and excitonic effects.

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Structure-Assigned Optical Spectra of Single-Walled Carbon Nanotubes

Graphene and related two-dimensional crystals and hybrid systems showcase several key properties that can address emerging energy needs, in particular for the ever growing market of portable and wearable energy conversion and storage devices. Graphene's flexibility, large surface area, and chemical stability, combined with its excellent electrical and thermal conductivity, make it promising as a catalyst in fuel and dye-sensitized solar cells. Chemically functionalized graphene can also improve storage and diffusion of ionic species and electric charge in batteries and supercapacitors. Two-dimensional crystals provide optoelectronic and photocatalytic properties complementing those of graphene, enabling the realization of ultrathin-film photovoltaic devices or systems for hydrogen production. Here, we review the use of graphene and related materials for energy conversion and storage, outlining the roadmap for future applications.

Graphene, related two-dimensional crystals, and hybrid systems for energy conversion and storage

We report gas and water flow measurements through microfabricated membranes in which aligned carbon nanotubes with diameters of less than 2 nanometers serve as pores. The measured gas flow exceeds predictions of the Knudsen diffusion model by more than an order of magnitude. The measured water flow exceeds values calculated from continuum hydrodynamics models by more than three orders of magnitude and is comparable to flow rates extrapolated from molecular dynamics simulations. The gas and water permeabilities of these nanotube-based membranes are several orders of magnitude higher than those of commercial polycarbonate membranes, despite having pore sizes an order of magnitude smaller. These membranes enable fundamental studies of mass transport in confined environments, as well as more energy-efficient nanoscale filtration.

http://science.sciencemag.org/content/sci/312/5776/1034.full.pdf

Fast Mass Transport Through Sub-2-Nanometer Carbon Nanotubes

Graphene and nanostructured MnO2 composite electrodes for supercapacitors

A B S T R A C T Graphene-based materials are promising electrodes for supercapacitors, owing to their unique two-dimensional structure, high surface area, remarkable chemical stability, and electrical conductivity In this paper, graphene is explored as a platform for energy storage devices by decorating graphenes with flower-like MnO 2 nanostructures fabricated by electrodeposition The as-prepared graphene and MnO 2, which were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), have been assembled into an asymmetric supercapacitor The specific capacitance of the graphene electrode reached 245 F/g at a charging current of 1 mA after an electro-activation process This value is more than 60% larger than the one before electro-activation The MnO 2 nano-flowers which consisted of tiny rods with a thickness of less than 10 nm were coated onto the graphene electrodes by electrodeposition The specific capacitance after the MnO 2 deposition is 328 F/g at the charging current of 1 mA with an energy density of 114 Wh/kg and 258 kW/kg of power density This work suggests that our graphene-based electrodes are a promising candidate for the high-performance energy storage devices

Graphene and nanostructured MnO 2 composite electrodes for supercapacitors

We describe a graphene and single-walled carbon nanotube (SWCNT) composite film prepared by a blending process for use as electrodes in high energy density supercapacitors. Specific capacitances of 290.6 F g−1 and 201.0 F g−1 have been obtained for a single electrode in aqueous and organic electrolytes, respectively, using a more practical two-electrode testing system. In the organic electrolyte the energy density reached 62.8 Wh kg−1 and the power density reached 58.5 kW kg−1. The addition of single-walled carbon nanotubes raised the energy density by 23% and power density by 31% more than the graphene electrodes. The graphene/CNT electrodes exhibited an ultra-high energy density of 155.6 Wh kg−1 in ionic liquid at room temperature. In addition, the specific capacitance increased by 29% after 1000 cycles in ionic liquid, indicating their excellent cyclicity. The SWCNTs acted as a conductive additive, spacer, and binder in the graphene/CNT supercapacitors. This work suggests that our graphene/CNT supercapacitors can be comparable to NiMH batteries in performance and are promising for applications in hybrid vehicles and electric vehicles.

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Graphene and carbon nanotube composite electrodes for supercapacitors with ultra-high energy density

We report here the discovery of the smallest possible carbon nanotube. This has a diameter of 4 A, which is the narrowest attainable that can still remain energetically stable, as predicted by theory. These nanotubes are confined inside multiwalled carbon nanotubes and their diameter corresponds to that of a C20 dodecahedron with a single carbon atom at each of its twenty apices. Unlike larger carbon nanotubes, which, depending on their diameter and helicity, can be either metallic or semiconducting, these smallest nanotubes are always metallic.

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The smallest carbon nanotube.

The transition from microcrystalline to nanocrystalline diamond films grown from Ar/H2/CH4 microwave plasmas has been investigated. Both the cross-section and plan-view micrographs of scanning electron microscopy reveal that the surface morphology, the grain size, and the growth mechanism of the diamond films depend strongly on the ratio of Ar to H2 in the reactant gases. Microcrystalline grain size and columnar growth have been observed from films produced from Ar/H2/CH4 microwave discharges with low concentrations of Ar in the reactant gases. By contrast, the films grown from Ar/H2/CH4 microwave plasmas with a high concentration of Ar in the reactant gases consist of phase pure nanocrystalline diamond, which has been characterized by transmission electron microscopy, selected area electron diffraction, and electron energy loss spectroscopy. X-ray diffraction and Raman spectroscopy reveal that the width of the diffraction peaks and the Raman bands of the as-grown films depends on the ratio of Ar to H2 in...

Lu Chang Qin

Papers

Graphene and nanostructured MnO2 composite electrodes for supercapacitors

Graphene and nanostructured MnO 2 composite electrodes for supercapacitors

Graphene and carbon nanotube composite electrodes for supercapacitors with ultra-high energy density

The smallest carbon nanotube.

Control of diamond film microstructure by Ar additions to CH4/H2 microwave plasmas