First-Principles Study of Carbon Nanoframeworks Tailored for Hydrogen Storage*

Based on first-principles calculations, we propose a novel class of 3-D materials consisting of small diameter single-walled carbon nanotubes (SWCNTs) functionalized by organic ligands as potential hydrogen storage media. Specifically, we have carried out density functional theory calculations to determine the stable structures and properties of nanoframeworks consisting of (5,0) and (3,3) SWCNTs constrained by phenyl spacers. Valence and conduction properties, as well as normal modes, of pristine nanotubes are found to change significantly upon functionalization, in a way that can serve as experimental diagnostics of the successful synthesis of the proposed framework structures. Ab initio molecular dynamics simulations indicate that such systems are thermodynamically stable for on-board hydrogen storage. In order to increase the hydrogen uptake in the interstitial cavity of such nanoframeworks, we are currently investigating the possibility of Li deposition on these nanostructures.