Titanium-capped carbon chains as promising new hydrogenstorage media

Abstract

The capacity of Ti-capped sp carbon atomic chains for use as hydrogen storage media is studied using first-principles density functional theory. The Ti atom is strongly attached at one end of the carbon chains via d-p hybridization, forming stable TiC_n complexes. We demonstrate that the number of adsorbed H₂ molecules on Ti through Kubas interactions depends upon the chain types. For polyyne (n even) or cumulene (n odd) structures, each Ti atom can hold up to five or six H₂ molecules, respectively. Furthermore, the TiC₅ chain effectively terminated on a C₂₀ fullerene can store hydrogen with an optimal binding energy of 0.52 eV per H₂ molecule. Our results reveal a possible way to explore high-capacity hydrogen storage materials in truly one-dimensional carbon structures.