  By employing the state-of-the-art density functional theory, we report the
hydrogen storage capability of yttrium decorated C$_{24}$ fullerene. Single Y
atom attached on C$_{24}$ fullerene can reversibly adsorb a maximum number of 6
H$_2$ molecules with average adsorption energy -0.37 eV and average desorption
temperature 477 K, suitable for fuel cell applications. The gravimetric weight
content of hydrogen is 8.84 %, which exceeds the target value of 6.5 wt % H by
the department of energy (DoE) of the United States. Y atom is strongly bonded
to C$_{24}$ fullerene with a binding energy of -3.4 eV due to a charge transfer
from Y-4d and Y-5s orbitals to the C-2p orbitals of C$_{24}$ fullerene. The
interaction of H$_2$ molecules with the Y atom is due to the Kubas type
interaction involving a charge donation from the metal d orbital to H 1s
orbital, and back donation causing slight elongation of H-H bond length. The
stability of the system at the highest desorption temperature is confirmed by
ab-initio molecular dynamics simulations, and the metal-metal clustering
formation has been investigated by computing the diffusion energy barrier for
the movement of Y atoms. We have corrected all the calculated energies for the
van der Waals (vdW) interactions by applying the dispersion energy corrections,
in addition to the contribution of the GGA exchange-correlation functional. The
C$_{24}$+Y system is stable at room temperature, and at the highest desorption
temperature, the presence of a sufficient diffusion energy barrier prevents
metal-metal clustering. Furthermore, binding energies of H$_2$ are within the
target value by DoE (-0.2-0.7 eV/H$_2$ ), while H$_2$ uptake (8.84 % H) is
higher than DoE's criteria. Therefore, we propose that Y decorated C$_{24}$
fullerene can be tailored as a practically viable potential hydrogen storage
candidate.
