Rapid, Room Temperature, High-Density Hydrogen Adsorption on Single-Walled Carbon Nanotubes at Atmospheric Pressure Assisted by a Metal Alloy

Laser-generated, carbon single-walled nanotubes (SWNTs) adsorb hydrogen in a matter of minutes at room temperature and atmospheric pressure in the presence of a Ti-6Al-4V metal alloy. The unusual hydrogen adsorption properties are activated when the SWNTs are sonicated in nitric acid with a Ti-6Al-4V probe. The process cuts the SWNTs and introduces ∼15-40 wt% metal alloy into the previously pure single-walled nanotube material. Subsequent hydrogen adsorption occurs in two separate sites with a maximum adsorption capacity of ∼7 wt% on a total sample weight basis. Approximately 2.5 wt% hydrogen is evolved at 300 K while the remainder desorbs between 475-850 K. The pure metal alloy adsorbs ∼2.5 wt% H₂, and evolves hydrogen with increasing temperature in a manner similar to the alloy-doped SWNTs. However, it is clear from studies presented here that the SWNT fraction is quite active in H₂ uptake, adsorbing as much as 7 % on a SWNT weight basis.