The adsorptions of H-2 on metallocarbohedrene Ti8Cl2, and nanocrystal Ti14C13 are studied using first-principles calculations. The Ti atoms serve as catalyst to mediate the dissociation of H-2 to form carbon hydrides, which otherwise would not form. Ti atoms on the surface of the nanocarbides are capable of coordinating with multiple dihydrogen ligands. High hydrogen capacities, 6.1 wt% for Ti8C12 and 7.7 wt% for Ti14C13, were obtained with more than 80% of the H bound in the energy range between 0.17 and 0.89 eV/ H-2. Once the nanoparticles form a macroscopic material, the amount of chemisorbed hydrogen decreases, but additional hydrogen molecules is then up-taken through physisorption. Our study suggests that TiC nanoparticles have potential for H storage at near ambient conditions. (c) 2006 Elsevier B.V. All rights reserved.