Formation of Graphitic Structures in Cobalt- and Nickel-Doped Carbon Aerogels

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 temperatu...

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Bibliographic Details
Published in:Langmuir 2005-03, Vol.21 (7), p.2647-2651
Main Authors: Fu, Ruowen, Baumann, Theodore F, Cronin, Steve, Dresselhaus, Gene, Dresselhaus, Mildred S, Satcher, Joe H
Format: Article
Language:English
Subjects:
Chemistry
Colloidal gels. Colloidal sols
Colloidal state and disperse state
Exact sciences and technology
General and physical chemistry
Physical and chemical studies. Granulometry. Electrokinetic phenomena
Porous materials
Surface physical chemistry
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Summary: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 °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 °C, respectively, forming nanoparticles that are ∼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 °C mainly consist of interconnected carbon particles with a size of 15−30 nm. When the samples are pyrolyzed at 1050 °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 ∼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.
ISSN:0743-7463
1520-5827
DOI:10.1021/la047344d