The effect of C-vacancy on hydrogen storage and characterization of H-2 modes on Ti functionalized C-60 fullerene A first principles study
Density functional theory calculations were performed to examine the effect of a C vacancy on the physisorption of H-2 onto Ti-functionalized C-60 fullerene when H-2 is oriented along the x-, y-, and z-axes of the fullerene. The effect of the C vacancy on the physisorption modes of H-2 was investigated as a function of H-2 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-2 in the defect-free (i.e., no C vacancy) C60TiH2 complex are along the x- and y-axes of C-60 (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) C59TiH2 complex do not exhibit adsorption energies within the targeted energy range. Charge transfer occurs from Ti 3d to C 2p of the fullerene. The binding of H-2 is dominated by the pairwise support-metal interaction energy E(i)(Cn...Ti), 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-2. A significant reduction in the energy gap of the pristine C-60 fullerene is observed when TiH2 is adsorbed by it. While the C (n) fullerene readily participates in nucleophilic processes, the adjacent TiH2 fragment is available for electrophilic processes.
hydrogen storage characterization c vacancy ti-functionalized fullerene