Mechanics of hydrogen storage in carbon nanotubes

A continuum mechanics model is established for hydrogen storage in single- and multi-wall carbon nanotubes (CNTs) and the bundle of single-wall CNTs. The model accounts for the deformation of CNTs, and van der Waals interactions among hydrogen molecules and between hydrogen and carbon atoms. The analytical expressions of hydrogen storage (number of hydrogen molecules per unit volume) in CNTs are obtained, and are validated by atomistic simulations. CNTs are categorized as tiny, small, medium and large CNTs; tiny CNTs cannot achieve the goals of hydrogen storage (62 kg/m³ and 6.5 wt% of hydrogen set by the US Department of Energy) without fracture; small CNTs are strained during hydrogen storage; medium CNTs can achieve the above goals without the strain and do not self collapse; and large CNTs may self collapse upon the release of hydrogen.