Formation of graphitic structures in cobalt- and nickel-doped carbon aerogels.

Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Langmuir (Impact Factor: 4.38). 04/2005; 21(7):2647-51. DOI: 10.1021/la047344d
Source: PubMed

ABSTRACT We have prepared carbon aerogels (CAs) doped with cobalt or nickel through sol-gel polymerization of formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by ion exchange with M(NO3)2 (where M = Co2+ or Ni2+), supercritical drying with liquid CO2, and carbonization at temperatures between 400 and 1050 degrees C under a N2 atmosphere. The nanostructures of these metal-doped carbon aerogels were characterized by elemental analysis, nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Metallic nickel and cobalt nanoparticles are generated during the carbonization process at about 400 and 450 degrees C, respectively, forming nanoparticles that are approximately 4 nm in diameter. The sizes and size dispersion of the metal particles increase with increasing carbonization temperatures for both materials. The carbon frameworks of the Ni- and Co-doped aerogels carbonized below 600 degrees C mainly consist of interconnected carbon particles with a size of 15-30 nm. When the samples are pyrolyzed at 1050 degrees C, the growth of graphitic nanoribbons with different curvatures is observed in the Ni- and Co-doped carbon aerogel materials. The distance of graphite layers in the nanoribbons is approximately 0.38 nm. These metal-doped CAs retain the overall open cell structure of metal-free CAs, exhibiting high surface areas and pore diameters in the micro- and mesoporic region.

1 Bookmark
  • [Show abstract] [Hide abstract]
    ABSTRACT: Three-dimensional, hierarchically ordered, porous carbon (HOPC) with designed porous textures, serving as an ion-buffering reservoir, an ion-transport channel, and a charge-storage material, is expected to be advanced an energy material for high-rate supercapacitors. Herein, HOPC without/with partially graphitic nanostructures have been directly synthesized by means of a simple one-pot synthesis procedure. The designed porous textures of the 3D HOPC materials are composed of highly ordered, fcc macroporous (300 nm), interconnected porous structures, including macroporous windows (170 nm), hexagonally ordered mesopores (5.0 nm), and useful micropores (1.2 nm). 3D HOPC-g-1000 (g=graphitic, 1000=pyrolysis temperature of 1000 °C) with partially graphitic nanostructures has a low specific surface area (296 m(2) g(-1)) and a low gravimetric specific capacitance (73.4 F g(-1) at 3 mV s(-1)), but improved electrical conductivity, better rate performance, higher electrolyte accessibility (24.8 μF cm(-2) at 3 mV s(-1)), faster frequency response (≈1 Hz), and excellent cycling performance (>5400 cycles). The specific capacitance per surface area is higher than that of conventional porous carbons, carbon nanotubes, and modified graphene (10-19 μF cm(-2)).
    ChemSusChem 03/2012; 5(3):563-71. · 7.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ordered mesoporous carbon materials have recently aroused great research interest because of their widespread applications in many areas such as adsorbents, catalysts and supports, gas storage hosts, and electrode materials. The direct synthesis strategy from organic-organic self-assembly involving the combination of polymerizable precursors and block copolymer templates is expected to be more flexible in preparing mesoporous carbons, compared with the traditional nanocasting strategy of complicated and high-cost procedures using mesoporous silica materials as the hard template. In this review, we present the fundamentals and recent advances related to the field of ordered mesoporous carbon materials from the direct synthesis strategy of block copolymer soft-templating, with a focus on their controllable preparation, modification and potential applications. Under the guidance of their formation mechanism, the preparation of ordered mesoporous carbons are discussed in detail by consulting different experimental conditions, including synthetic pathways, precursors, catalysts and templates. Both the mesopore size and morphology control are introduced. The potential applications of pure mesoporous carbons, nonmetallic- and metallic-modified mesoporous carbons, and some interpenetrating carbon-based composites are demonstrated. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of the ordered mesoporous carbons (232 references).
    Chemical Society Reviews 11/2012; 42(9):3977-4003. · 24.89 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nanoporous carbon particles with magnetic Co nanoparticles (Co/NPC particles) are synthesized by one-step carbonization of zeolitic imidazolate framework-67 (ZIF-67) crystals. After the carbonization, the original ZIF-67 shapes are preserved well. Fine magnetic Co nanoparticles are well dispersed in the nanoporous carbon matrix, with the result that the Co/NPC particles show a strong magnetic response. The obtained nanoporous carbons show a high surface area and well-developed graphitized wall, thereby realizing fast molecular diffusion of methylene blue (MB) molecules with excellent adsorption performance. The Co/NPC possesses an impressive saturation capacity for MB dye compared with the commercial activated carbon. Also, the dispersed magnetic Co nanoparticles facilitate easy magnetic separation.
    Small 03/2014; · 7.82 Impact Factor