Adsorption of Hydrogen on Carbon Single-Walled Nanotubes as Measured by the Volumetric Technique

We report on hydrogen adsorption onto carbon single-walled nanotube (SWNT) material as measured by the volumetric technique. This method determines the amount adsorbed by monitoring the pressure in a known volume at a known temperature with a given number of moles of hydrogen introduced. The raw material for the samples is produced by pulsed laser vaporization of a graphite target containing Ni (0.6 at%) and Co (0.6 at%) dopants. This is followed with a purification procedure and then by a cutting procedure. Finally, the sample is degassed before the hydrogen adsorption is measured. The cutting procedure introduces a titanium alloy which participates in the overall hydrogen adsorption of the SWNT material. Importantly though, the amount of hydrogen adsorbed in the SWNT material cannot be explained by absorption from the alloy alone. A description of the apparatus that has allowed us to measure these samples is given and we discuss crucial experimental procedures needed to activate the SWNT samples for hydrogen adsorption.