Synthesis and hydrogen storage of carbon nanofibers and single-walled carbon nanotubes

This paper overviews the research work of the authors in the field of synthesis and hydrogen storage measurements of various types of carbon nanostructures. Single-walled carbon nanotubes (SWNTs) and carbon nanofibers (CNFs) were synthesized by a catalytic pyrolysis method. Macroscopic ropes and ribbons of SWNT bundles with a rope diameter of about 100 microns and lengths to 30 mm can be synthesized by this method. Microstructure observations by TEM show that these ropes and ribbons consist of roughly aligned bundles and the bundles consist of well-aligned SWNTs. Moreover, a high yield, up to gram quantities of SWNTs per hour, can be achieved with a semi-continuous hydrogen electric arc discharge method. Based on Raman scattering results, our SWNTs are found to have a wider diameter distribution and a larger mean diameter than those of commonly grown SWNTs. The hydrogen uptake measurements of CNFs and SWNTs were carried out using a high-pressure volumetric method. The preliminary results show that, after suitable pretreatment, both CNFs and SWNTs can store 4 wt.% or higher of hydrogen, which may imply a great potential for applications of these materials in fuel cell-driven vehicles.