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Synthesis of carbon nanotube–TiO2 nanotubular material for reversible hydrogen storage

A material consisting of multi-walled carbon nanotubes (MWCNTs) and larger titania (TiO2) nanotube arrays has been produced and found to be efficient for reversible hydrogen (H2) storage. The TiO2 nanotube arrays (diameter ∼60 nm and length ∼2–3 µm) are grown on a Ti substrate, and MWCNTs a few µm in length and ∼30–60 nm in diameter are grown inside these TiO2 nanotubes using chemical vapor deposition with cobalt as a catalyst. The resulting material has been used in H2 storage experiments based on a volumetric method using the pressure, composition, and temperature relationship of the storage media. This material can store up to 2.5 wt% of H2 at 77 K under 25 bar with more than 90% reversibility.