Effect of MoO 3 as conditioning catalyst on synthesis of carbon nanotubes
- PDF / 1,192,330 Bytes
- 4 Pages / 584.957 x 782.986 pts Page_size
- 4 Downloads / 202 Views
Effect of MoO3 as conditioning catalyst on synthesis of carbon nanotubes Yunfang Liu, Kenji Takeuchi, Ki Chul Park, and Hiroyuki Muramatsu Faculty of Engineering, Shinshu University, Nagano-shi 380-8553, Japan
Tomoyuki Fukuyo MEFS Co., Ltd., Nagano-shi 380-0921, Japan
Morinobu Endoa) Faculty of Engineering, Shinshu University, Nagano-shi 380-8553, Japan (Received 22 June 2008; accepted 20 November 2008)
The effect of nonsupported MoO3 as a conditioning catalyst on the preparation of carbon nanotubes (CNTs) using a common main catalyst Fe/MgO was investigated. Without using MoO3, only single-walled CNTs were produced at low yield. In contrast, the use of MoO3 provided single-walled and double-walled CNTs at high yield. The MoO3 conditioning catalyst enhances not only the yield but also the diameter and layer number of CNTs. The higher yield formation of more layered CNTs with larger diameter would be attributed to the preproduction of reactive hydrocarbon species by the conditioning catalyst and their growth to larger molecular-weight reactive species. In the synthesis of carbon nanotubes (CNTs), reactive hydrocarbon species as precursor of graphene is one of the important key factors that could affect not only the yield but also the structure of CNTs. Many methods have been attempted to get different carbon species for the preparation of CNTs by changing catalysts and hydrocarbons as carbon sources. Molybdenum (Mo) has been widely used as a catalyst for preparing CNTs. Although there was an attempt to use Mo as a main catalyst for CNT growth,1 most researchers used it as one ingredient in bimetallic or multimetallic catalyst systems.2,3 Dai et al. used Fe-Mo/Al2O3 as a conditioning catalyst to enhance the yield of SWNT efficiently.4 Endo et al. used Mo/Al2O3 as a conditioning catalyst to preferentially synthesize high-quality DWNTs.5,6 As reported previously, MoO3-containing catalysts are highly effective for refinement and de-hydroaromatization of simple aliphatic hydrocarbons such as CH4 into aromatics such as benzene.7,8 Therefore, it is likely that the reactive hydrocarbon species promoted by the Mobased conditioning catalysts largely contribute to the production of CNTs. To our knowledge, however, there are few reports that make systematic investigation about the role of Mo-based conditioning catalysts in the CNT production. Herein, we first discuss the role of Mo-based conditioning catalyst in the CNT synthesis using ordinary Fe/MgO as a main catalyst. For simplicity, nonsupported a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0150 J. Mater. Res., Vol. 24, No. 4, Apr 2009
http://journals.cambridge.org
Downloaded: 18 Mar 2015
MoO3 was used to exclude the support’s influence on preparing CNTs. Based on the results of high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), and Raman spectroscopy analyses possible effect of Mobased conditioning catalyst was discussed. The main catalys
Data Loading...
