Annealing amorphous carbon nanotubes for their application in hydrogen storage

Carbon nanotubes with poor crystallization degree were mass-produced by the floating catalyst method, and their crystallizing procedure at high annealing temperatures were investigated. The crystallization behavior is different from that of bulk amorphous carbons due to the finite dimensions and tube-like shape of the as-grown carbon nanotubes. Further hydrogen adsorption experiments showed that the as-grown carbon nanotubes have poor hydrogen up-take capacity at room temperature under modest pressure (10 MPa), however, the hydrogen storage amount was improved remarkably in the annealed carbon nanotubes at temperature range 1700-2200 °C. The reason for the improved hydrogen storage capacity was discussed according to the changes in their surface feature and microstructure during the annealing procedure.