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 C_(20) 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.
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