부산대학교 도서관

Density functional theory calculations were performed to examine the effect of a C vacancy on the physisorption of H onto Ti-functionalized C fullerene when H is oriented along the x-, y-, and z-axes of the fullerene. The effect of the C vacancy on the physisorption modes of H was investigated as a function of H binding energy within the energy window (−0.2 to −0.6 eV) targeted by the Department of Energy (DOE), and as functions of a variety of other physicochemical properties. The results indicate that the preferential orientations of H in the defect-free (i.e., no C vacancy) CTiH complex are along the x- and y-axes of C (with adsorption energies of −0.23 and −0.21 eV, respectively), making these orientations the most suitable ones for hydrogen storage, in contrast to the results obtained for defect-containing fullerenes. The defect-containing (i.e., containing a C vacancy) CTiH complex do not exhibit adsorption energies within the targeted energy range. Charge transfer occurs from Ti 3 d to C 2 p of the fullerene. The binding of H is dominated by the pairwise support-metal interaction energy E(i), and the role of the fullerene is not restricted to supporting the metal. The C vacancy enhances the adsorption energy of Ti, in contrast to that of H. A significant reduction in the energy gap of the pristine C fullerene is observed when TiH is adsorbed by it. While the C fullerene readily participates in nucleophilic processes, the adjacent TiH fragment is available for electrophilic processes. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]