Optimization of Single-Wall Nanotube Synthesis For Hydrogen Storage

摘要

Carbon single-wall nanotubes (SWNTs) are capable of adsorbing hydrogen quickly, to high density, at ambient temperatures and pressures. Last year, we showed that hydrogen storage densities on SWNTs made by laser vaporization ranged from 3.5 to 4.5 wt% after a cutting procedure was performed. We present details of the cutting procedure here and show that, when optimized, hydrogen storage densities up to 7 wt% can be achieved. Infrared absorption spectroscopy measurements on pristine and H2-charged samples indicate that no C-H bonds are formed in the process. These experiments are in agreement with an earlier temperature programmed desorption analysis that showed that hydrogen molecules are not dissociated when bound to the SWNT surfaces. All in all, we find that the interaction between H2 and single-wall nanotubes is mid-way between conventional van der Waals adsorption and chemical bond formation. A detailed understanding of the mechanism coupled with a high degree of control during synthesis should allow useful hydrogen adsorbents to be designed and constructed.