Characterization and preparation of single wall nanotubes for hydrogen storage

In the recent years, some works mentioned that hydrogen storage densities on SWNTs made by laser vaporization ranged from 3.5 to extreme 4.5 wt% after a new cutting procedure was performed. Infrared absorption spectroscopy measurements on pristine and H2-charged samples indicate that no C-H bonds are formed in the hydrogen adsorption process. These experiments are in agreement with an earlier temperature programmed desorption analysis which showed that hydrogen molecules are not dissociated when bound to the SWNT surfaces. Carbon single-wall nanotubes (SWNTs) are capable for quickly hydrogen adsorbing, in high density, at ambient temperatures and pressures. We present in details the cutting procedure and show that after optimization, hydrogen storage densities can be achieved up to 7 wt%. Raman spectroscopy indicated that the as produced materials were ~ 50 wt% pure SWNTs, in contrast to the 20 to 30 wt% usually seen with the previous laser, and the production rate for raw soot appears to be significantly greater than the 150 mg/hr that observed previously, even though the current performance is probably far from optimal. We present results from experiments designed to elucidate the mechanisms responsible for the unique hydrogen adsorption properties.