The role of carbon nanotube structure in purification and hydrogen adsorption

Structural properties of carbon nanotubes were studied by using samples from various manufacturers synthesized by different processes. A two-stage purification method was applied to all samples. Relationships between synthesis techniques and carbon nanotube structure are discussed. The role of carbon nanotube structural features such as degree of crystallinity, tube diameter, tube wall structure, and bundling behavior in purification and hydrogen adsorption were investigated by a combination of transmission electron microscopy and magnetic resonance techniques. It is suggested that MWNTs with low crystallinity and SWNTs with large diameters and open tube ends yielded the highest hydrogen uptake capacities. Both MWNTs and SWNTs show low hydrogen storage capacities (less than 1 wt%) at hydrogen pressures up to 1480 kPa.