Energy Fuels 2010, 24, 3361–3365 Published on Web 03/10/2010
: DOI:10.1021/ef9015119
Study of the Synthesis Conditions of Carbon Nanocoils for Energetic Applications† V. Celorrio,‡ L. Calvillo,‡ M. V. Martı´ nez-Huerta,§ R. Moliner,‡ and M. J. Lazaro*,‡ ‡
Instituto de Carboquı´mica, Consejo Superior de Investigaciones Cientı´ficas (CSIC), Miguel Luesma Cast an 4, 50018 Zaragoza, Spain, and §Instituto de Cat alisis y Petroleoquı´mica, Consejo Superior de Investigaciones Cientı´ficas (CSIC), Marie Curie 2, 28049 Madrid, Spain Received December 10, 2009. Revised Manuscript Received February 25, 2010
The synthesis of carbon nanocoils (CNCs) by the catalytic graphitization of composites has been studied. Resorcinol-formaldehyde gel was used as the carbon precursor; a mixture of cobalt and nickel salts was used as the graphitization catalysts in the synthesis; and silica sol was added to the reaction mixture to obtain carbon materials with high specific surface area and to achieve a good dispersion of the transitionmetal nanoparticles. Different molar ratios of the reagents were used with the purpose of obtaining carbon materials with different structural and textural properties, seeking a compromise between the graphitization degree and surface area. X-ray diffraction (XRD), Raman spectrometry, transmission electron microscopy (TEM), temperature-programmed oxidation (TPO), N2 physisorption, and temperatureprogrammed desorption (TPD) were used to characterize the morphology, textural properties, and surface chemistry of such materials. Results showed that obtained CNCs had good crystallinity and well-defined porosity, which depended upon the preparation conditions.
Many forms of graphitic nanostructured carbon materials, including carbon nanotubes, graphitic carbon nanofibers, and carbon nanocoils (CNCs), can be produced using various gasphase reactions.10,11 Among these materials, CNCs have recently received tremendous attention because of the combination of their good electrical conductivity, derived from their graphitic structure, and a wide porosity that allows for the diffusional resistances of reactants/products to be minimized. Nevertheless, the methods to synthesize them, such as arc discharge,12 laser vaporization,13 and thermal chemical vapor deposition,14 have limitations in terms of large-scale and economical production because of the high temperatures that they need (arc discharge, 5000-20000 °C; laser vaporization, 4000-5000 °C). Therefore, taking these drawbacks into consideration, a solid-phase synthetic procedure has to be developed.15,16 Although several groups have reported the solid-phase synthesis of nanostructured graphitic carbon materials, the synthetic processes used cannot be applied for economical and large-scale applications because of the long reaction time and/ or a complicated synthesis procedure. Synthetic graphites are all basically prepared by heating unstructured carbon at temperatures over 2500 °C. This heat treatment orients the disordered layers into the graphitic structure. Dependent upon the raw material used and the heat treatment process, the characteristics of the synthetic graphite differ.
1. Introduction 1
Since the discovery of carbon nanotubes by Iijima, much attention has been paid to the design of nanostructured graphitic carbon materials. Today graphite is the most important carbon in electrochemical applications because of its unique properties. Their high electrical conductivity, thermal stability, and chemical inertness make possible their use as catalytic supports,2,3 nanocomposites,4-6 and electrode materials.7,8 The carbonaceous graphitic materials used as electrode materials in electrochemical devices must possess a high specific surface and porosity, high resistance to corrosion, high thermal stability, and relatively low cost, as well as high electrical conductivity.9 On the other hand, these materials must have specific properties for the type of electrochemical device in which they work. † This paper has been designated for the special section Carbon for Energy Storage and Environment Protection. *To whom correspondence should be addressed: Instituto de Carboquı´ mica, Consejo Superior de Investigaciones Cientı´ ficas (CSIC), Miguel Luesma Cast an 4, 50018 Zaragoza, Spain. Telephone: þ34976733977. Fax: þ34-976733318. E-mail:
[email protected]. (1) Iijima, S. Nature 1991, 354, 56–58. (2) Moliner, R.; L azaro, M. J.; Calvillo, L.; Sebastian, D.; Echegoyen, Y; Garcı´ a-Bordeje, E.; Salgado, J. R. C.; Pastor, E.; Cabot, P. L.; Esparbe, I. Sens. Lett. 2008, 6, 1–9. (3) Sevilla, M.; Lota, G.; Fuertes, A. B. J. Power Sources 2007, 171, 546–551. (4) Hammel, E.; Tang, X.; Trampert, M.; Schmitt, T.; Mauthner, K.; Eder, A.; P€ otschke, P. Carbon 2004, 42, 1153–1158. (5) Tibbetts, G. G.; Lake, M. L.; Strong, K. L.; Rice, B. P. Compos. Sci. Technol. 2007, 67, 1709–1718. (6) Vera-Agullo, J.; Gl oria-Pereira, A.; Varela-Rizo, H.; Gonzalez, J. L.; Martin-Gullon, I. Compos. Sci. Technol. 2009, 69, 1521–1532. (7) Hyeon, T.; Han, S.; Sung, Y. E.; Park, K. W.; Kim, Y. W. Angew. Chem., Int. Ed. 2003, 42, 4352–4356. (8) Pico, F.; Iba~ nez, J.; Lillo-Rodenas, M. A.; Linares-Solano, A.; Rojas, R. M.; Amarilla, J. M.; Rojo, J. M. J. Power Sources 2008, 176, 417–425. (9) Pandolfo, A. G.; Hollenkmp, A. F. J. Power Sources 2006, 157, 11–27.
r 2010 American Chemical Society
(10) Zhao, D. L.; Shen, Z. M. Mater. Lett. 2008, 62, 3704–3706. (11) Pinilla, J. L.; Moliner, R.; Suelves, I.; Lazaro, M. J.; Echegoyen, Y.; Palacios, J. M. Int. J. Hydrogen Energy 2007, 32, 4821–4829. (12) Ugarte, D. Carbon 1995, 33, 989–993. (13) Guo, T.; Nicolaev, P.; Thess, A.; Colbert, D. T.; Smalley, R. E. Chem. Phys. Lett. 1995, 243, 49–54. (14) Yang, S.; Chen, X.; Katsuno, T.; Motojima, S. Mater. Res. Bull. 2007, 42, 465–473. (15) Han, S.; Yun, Y.; Park, K. W.; Sung, Y. E.; Hyeon, T. Adv. Mater. 2003, 15, 1922–1925. (16) Sevilla, M.; Fuertes, A. B. Mater. Chem. Phys. 2008, 113, 208– 214.
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Energy Fuels 2010, 24, 3361–3365
: DOI:10.1021/ef9015119
Celorrio et al.
In recent years, the phenomena of catalytic graphitization have been developed considerably. The use of transition metals or their inorganic compounds to promote graphitization at lower temperatures represents an attractive alternative. Several reviews of catalytic graphitization are available in the literature.16,17 Among metals that act as catalysts are certain transition metals, such as nickel,18,19 iron, cobalt, manganese,19 aluminum,20 etc. Normally, catalytic graphitization lies in improving the crystalinity of a carbon material by the formation of graphitic material. This process involves a chemical reaction between the ungraphitized carbon and the metal or inorganic compound, which acts as the graphitization catalyst.21-23 Its main advantage is that both graphitizing and non-graphitizing carbons can be transformed into crystalline materials at relatively low temperatures (T < 1000 °C), whereas uncatalysed graphitization requires the use of temperatures greater than 2000-2500 °C and carbon precursors that have graphitizable properties. In this work, the catalytic graphitization is proposed as the synthesis procedure for CNCs; this way, carbon materials containing graphitic structures can be obtained at low temperature (
